AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

Exhibit 4.8

AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

This REGISTRATION RIGHTS AGREEMENT (as it may be amended from time to time in accordance with the terms hereof, the “Agreement”), dated as of [ ], 2014, is made by and among Trinseo S.A., a public limited liability company (société anonyme) existing under the laws of the Grand Duchy of Luxembourg (the “Company”) and Bain Capital Everest Manager Holding S.C.A., a société en commandite par actions existing under the laws of the Grand Duchy of Luxembourg (the “Investor”) such other Persons, if any, that from time to time become party hereto as holders of Registrable Securities in their capacity as Permitted Transferees (together with the Investor, the “Investors”).

RECITALS

WHEREAS, the Company has filed a registration statement on Form S-1 to initiate an initial public offering of Ordinary Shares; and

WHEREAS, the Investor, as of the date hereof, is the sole shareholder of the Company and the parties believe that it is in the best interests of the Company and the other parties hereto to set forth their agreements regarding registration rights.

NOW, THEREFORE, in consideration of the foregoing and the mutual promises, covenants and agreements of the parties hereto, and for other good and valuable consideration, the receipt and sufficiency of which is hereby acknowledged, the parties hereto agree as follows:

AGREEMENT

Therefore, the parties hereto hereby agree as follows:

1.1. Closing. This Agreement shall become effective immediately upon signing.

1.2. Definitions. Certain terms are used in this Agreement as specifically defined herein. These definitions are set forth or referred to in Section 5 hereof.

2.1. Demand Registration Rights for Investor Registrable Securities.

2.1.1. General. One or more Investors, by notice to the Company specifying the intended method or methods of disposition, may request that the Company effect the registration under the Securities Act for a Public Offering of all or a specified part of the Registrable Securities held by such Investors. The Company will then use its best efforts to (i) effect the registration under the Securities Act (including by means of a

shelf registration pursuant to Rule 415 under the Securities Act if requested by the Participating Investors and if the Company is then eligible to use such registration) of the Registrable Securities that the Company has been requested to register by such Investors together with all other Registrable Securities that the Company has been requested to register pursuant to Section 2.2 by other Holders, and (ii) if requested by the Participating Investors, obtain acceleration of the effective date of the registration statement relating to such registration; provided, however, that the Company shall not be obligated to take any action to effect any such registration pursuant to this Section 2.1.1:

(a) during the effectiveness of any Lock-Up Agreement entered into in connection with any registration statement pertaining to an underwritten public offering of securities of the Company for its own account (other than a Rule 145 Transaction, or a registration relating solely to employee benefit plans);

(b) if a registration statement requested under this Section 2.1.1 became effective within the preceding 60 days.

2.1.2. Form. Except as otherwise provided above or required by law, each registration requested pursuant to Section 2.1.1 shall be effected by the filing of a registration statement on Form S-3 (or any successor or similar form which includes substantially the same information as would be required to be included in a registration statement on such form as currently constituted), if the Company is then eligible to use such registration; provided that (x) if any registration requested pursuant to this Section 2.1 is proposed to be effected on Form S-3 (or any successor or similar shortform registration statement) and (i) the Company is not then eligible to use such registration or (ii) the registration is in connection with an underwritten offering, and if the managing underwriter shall advise the Company in writing that, in its opinion, it is of material importance to the success of such proposed offering to file a registration statement on Form S-1 (or any successor or similar registration statement) or to include in such registration statement information not required to be included pursuant to Form S-3 (or any successor or similar shortform registration statement), then (y) the Company will file a registration statement on Form S-1 or supplement Form S-3 (or any successor or similar shortform registration statement) as reasonably requested.

2.1.3. Payment of Expenses. The Company shall pay all Registration Expenses in connection with registrations of Registrable Securities pursuant to this Section 2.1.

2.1.4. Additional Procedures. If requested by the Participating Investors, the Company will enter into an underwriting agreement with the underwriters for such offering containing such representations and warranties by the Company and such Holders and such other terms and provisions as are customarily contained in underwriting agreements with respect to secondary distributions, including customary indemnity and contribution provisions (subject, in each case, to the limitations on such liabilities set forth in this Agreement).

2.1.5. Suspension of Registration. If the filing, initial effectiveness or continued use of a registration statement, including a shelf registration statement pursuant to Rule 415 under the Securities Act, in respect of a registration pursuant to this Section 2.1 at any time would require the Company to make a public disclosure of material non-public information, which disclosure in the good faith judgment of the Board (after consultation with external legal counsel) (i) would be required to be made in any registration statement so that such registration statement would not be materially misleading, (ii) would not be required to be made at such time but for the filing, effectiveness or continued use of such registration statement and (iii) would have a material adverse effect on the Company or its business or on the Company’s ability to effect a material proposed acquisition, disposition, financing, reorganization, recapitalization or similar transaction, then the Company may, upon giving prompt written notice of such action to the Holders participating in such registration, delay the filing or initial effectiveness of, or suspend use of, such registration statement; provided, that the Company shall not be permitted to do so (i) more than two times during any 12 month period, (ii) for a period exceeding 30 days on any one occasion or (iii) for a period exceeding 60 days in any 12 month period. In the event the Company exercises its rights under the preceding sentence, such Holders agree to suspend, promptly upon their receipt of the notice referred to above, their use of any prospectus relating to such registration in connection with any sale or offer to sell Registrable Securities. The Company shall promptly notify such Holders of the expiration of any period during which it exercised its rights under this Section 2.1.5. The Company agrees that, in the event it exercises its rights under this Section 2.1.5, it shall, within 30 days following such Holders’ receipt of the notice of suspension, update the suspended registration statement as may be necessary to permit the Holders to resume use thereof in connection with the offer and sale of their Registrable Securities in accordance with applicable law.

2.2. Piggyback Registration Rights.

2.2.1. Piggyback Registration.

(a) General. Each time the Company proposes to register any Ordinary Shares under the Securities Act on a form which would permit registration of Registrable Securities for sale to the public for its own account and/or for the account of any other Person (pursuant to Section 2.1 or otherwise) for sale in a Public Offering (including each time the Company proposes to offer Ordinary Shares to the public for its own account and/or for the account if any other Person pursuant to an effective shelf registration statement pursuant to Rule 415 under the Securities Act), the Company will give notice to all Holders of its intention to do so. Any Holder may, by written response delivered to the Company within 10 days after the date of delivery of such notice (or such shorter period as may reasonably be requested in connection with the filing of any automatically effective registration statement), request that all or a specified part of such Holder’s Registrable Securities be included in such registration. The Company thereupon will use its reasonable best efforts to cause to be included in such registration under the Securities Act all Registrable Securities which the Company

has been so requested to register by such Holders, to the extent required to permit the disposition (in accordance with the methods to be used by the Company or, pursuant to Section 2.1, other Holders in such Public Offering) of the Registrable Securities to be so registered; provided that (i) if, at any time after giving written notice of its intention to register any securities, the Company shall determine for any reason not to proceed with the proposed registration of the securities, the Company may, at its election, give written notice of such determination to each Holder and, thereupon, shall be relieved of its obligation to register any Registrable Securities in connection with such registration pursuant to this Section 2.2.1 (but not from its obligation to pay the Registration Expenses in connection therewith), and (ii) if such registration involves an underwritten offering, all Holders requesting to be included in such registration and electing to participate in such underwritten offering must sell their Registrable Securities to the underwriters on the same terms and conditions as apply to the Company (with such differences as may be customary or appropriate in combined primary and secondary offerings), or, in the case of any registration requested pursuant to Section 2.1, the Participating Investors. No registration of Registrable Securities effected under this Section 2.2 shall relieve the Company of any of its obligations to effect registrations of Registrable Securities pursuant to Section 2.1 hereof.

(b) Excluded Transactions. The Company shall not be obligated to effect any registration of Registrable Securities under this Section 2.2 incidental to the registration of any of its securities in connection with:

(i) Any Public Offering relating to employee benefit plans or dividend reinvestment plans; or

(ii) Any Public Offering relating to the acquisition or merger after the date hereof by the Company or any of its subsidiaries of or with any other businesses except to the extent such Public Offering is for the sale of securities in cash.

2.2.2. Payment of Expenses. The Company will pay all Registration Expenses in connection with registrations of Registrable Securities pursuant to this Section 2.2.

2.2.3. Additional Procedures. Holders participating in any Public Offering pursuant to this Section 2.2 shall take all such actions and execute all such documents and instruments that are reasonably requested by the Company to effect the sale of their Registrable Securities in such Public Offering, including being parties to the underwriting agreement entered into by the Company and any other selling shareholders in connection therewith and being liable in respect of the representations and warranties and the other agreements (including customary selling shareholder representations, warranties, indemnifications and “lock-up” agreements) for the benefit of the underwriters contained therein; provided, however, that with respect to individual representations, warranties, indemnities and agreements of sellers of Registrable Securities contained in such underwriting agreement, the aggregate amount of such liability (including contribution) thereunder shall be several and not joint and shall not exceed such holder’s net proceeds from such offering.

2.2.4. Registration Statement Form. The Company shall select the registration statement form for any registration pursuant to this Section 2.2 (other than a registration that is also pursuant to Section 2.1); provided that if any registration requested pursuant to this Section 2.2 is proposed to be effected on Form S-3 (or any successor form) and is in connection with an underwritten offering, and if the managing underwriter shall advise the Company in writing that, in its opinion, it is of material importance to the success of such proposed offering to include in such registration statement information not required to be included pursuant to such form, then the Company will supplement such registration statement as reasonably requested by such managing underwriter.

2.3. Certain Other Provisions.

2.3.1. Underwriter’s Cutback. In connection with any registration of shares, the underwriter may determine that marketing factors (including an adverse effect on the per share offering price) require a limitation of the number of shares to be underwritten. Notwithstanding any contrary provision of this Section 2 and subject to the terms of this Section 2.3.1, the underwriter may limit the number of shares which would otherwise be included in such registration by excluding Registrable Securities from such registration, it being understood that, if the registration in question involves a registration for sale of securities for the Company’s own account, then the number of shares which the Company seeks to have registered in such registration shall not be subject to exclusion, in whole or in part, under this Section 2.3.1. Upon receipt of notice from the underwriter of the need to reduce the number of shares to be included in the registration, the Company shall advise all holders of the Company’s securities that would otherwise be registered and underwritten pursuant hereto, and the number of shares of such securities, including Registrable Securities, that may be included in the registration shall be allocated in the following manner, unless the underwriter shall determine that marketing factors require a different allocation: shares, other than Registrable Securities, requested to be included in such registration by other shareholders shall be excluded unless the Company, with the consent of the parties required to approve any amendment or waiver of this Agreement pursuant to Section 4.2, has granted registration rights which are to be treated on an equal basis with Registrable Securities for the purpose of the exercise of the underwriter cutback (such shares afforded such equal treatment being “Parity Shares”); and, if a limitation on the number of shares is still required, the number of Registrable Securities, Parity Shares and other Ordinary Shares that may be included in such registration shall be allocated among the holders thereof in proportion, as nearly as practicable, as follows:

(a) there shall be first allocated to each such Holder requesting that its Registrable Securities or Parity Shares be registered in such registration a number of such shares to be included in such registration equal to the lesser of (A) the number of such shares requested to be registered by such holder, and (B) a number of such shares equal to such holder’s Pro Rata Portion;

(b) the balance, if any, not allocated pursuant to clause (a) above shall be allocated to those holders requesting that their Registrable Securities or Parity Shares be registered in such registration which requested to register a number of such shares in excess of such holder’s Pro Rata Portion pro rata to each such holder based upon the number of Registrable Securities and Parity Shares held by such holder, or in such other manner as the holders requesting that their Registrable Securities or Parity Shares be registered in such registration may otherwise agree; and

(c) the balance, if any, not allocated pursuant to clause (b) above shall be allocated to shares, other than Registrable Securities and Parity Shares, requested to be included in such registration by other shareholders.

No securities excluded from the underwriting by reason of the underwriter’s marketing limitation shall be included in such registration.

2.3.2. Restrictions on withdrawal from certain registrations. A written request that Registrable Securities be included in the underwriting pursuant to Section 2.1.1 or 2.2.1(a) in connection with any overnight “block trade” conducted as a Public Offering, shall be binding on the Participating Investor, provided that each Participating Investor that elects to participate in any such registration may condition its participation on such registration being completed within ten (10) trading days of its acceptance at a price per share (after giving effect to any underwriters’ discounts or commissions) to such Participating Investor of not less than ninety-two percent (92%) of the closing price for the shares on their principal trading market on the trading day immediately prior to such Participating Investor’s election to participate.

2.3.3. Registration Procedures. If, and in each case when, the Company is required to effect a registration of any Registrable Securities as provided in this Section 2, the Company shall promptly:

(a) prepare and, in any event within forty-five days (five days in the case of a Form S-3 registration) after the end of the period under Section 2.2.1(a) within which a piggyback request for registration may be given to the Company, file with the Commission a registration statement with respect to such Registrable Securities and use its reasonable best efforts to cause such registration statement to become effective as promptly as practicable and in any event within ninety days of the initial filing;

(b) prepare and file with the Commission such amendments and supplements to such registration statement and the prospectus used in connection therewith as may be necessary to keep such registration statement effective for a period not in excess of 270 days (or such shorter period which will terminate when all Registrable Securities covered by such registration statement have been sold) and to comply with the provisions of the Securities Act and the Exchange Act with respect to the disposition of all securities covered by such registration statement during such period in accordance with the intended methods of

disposition by the seller or sellers thereof set forth in such registration statement; provided that before filing a registration statement or prospectus, or any amendments or supplements thereto in accordance with Sections 2.1 or 2.2, the Company will furnish to counsel selected pursuant to Section 2.3.3 hereof copies of all documents proposed to be filed, which documents will be subject to the review and comment of such counsel;

(c) furnish to each seller of such Registrable Securities such number of copies of such registration statement and of each amendment and supplement thereto (in each case including all exhibits filed therewith), such number of copies of the prospectus included in such registration statement (including each preliminary prospectus and summary prospectus), in conformity with the requirements of the Securities Act, and such other documents as such seller may reasonably request in order to facilitate the disposition of the Registrable Securities by such seller;

(d) use its reasonable best efforts to register or qualify such Registrable Securities covered by such registration in such jurisdictions as each seller shall reasonably request, and do any and all other acts and things which may be reasonably necessary or advisable to enable such seller to consummate the disposition in such jurisdictions of the Registrable Securities owned by such seller, except that the Company shall not for any such purpose be required to qualify generally to do business as a foreign corporation in any jurisdiction where, but for the requirements of this clause (d), it would not be obligated to be so qualified or to consent to general service of process in any such jurisdiction;

(e) notify each seller of any such Registrable Securities covered by such registration statement, at any time when a prospectus relating thereto is required to be delivered under the Securities Act, of the Company’s becoming aware that the prospectus included in such registration statement, as then in effect, includes an untrue statement of a material fact or omits to state a material fact required to be stated therein or necessary to make the statements therein not misleading in the light of the circumstances then existing, and at the request of any such seller, prepare and furnish to such seller a reasonable number of copies of an amended or supplemental prospectus as may be necessary so that, as thereafter delivered to the purchasers of such Registrable Securities, such prospectus shall not include an untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading in the light of the circumstances then existing;

(f) otherwise use its reasonable best efforts to comply with all applicable rules and regulations of the Commission, and make available to its security holders, as soon as reasonably practicable (but not more than 18 months) after the effective date of the registration statement, an earnings statement which shall satisfy the provisions of Section 11(a) of the Securities Act;

(g) (i) if such Registrable Securities are Ordinary Shares (including Ordinary Shares issuable upon conversion, exchange or exercise of another security), use its reasonable best efforts to list such Registrable Securities on any securities exchange on which the Ordinary Shares are then listed; and (ii) use its reasonable best efforts to provide a transfer agent and registrar for such Registrable Securities covered by such registration statement not later than the effective date of such registration statement;

(h) enter into such customary agreements (including an underwriting agreement in customary form), which may include indemnification provisions in favor of underwriters and other Persons, subject to Section 2.2.3 , and take such other actions as the Participating Investors or the underwriters, if any, reasonably requested in order to expedite or facilitate the disposition of such Registrable Securities;

(i) obtain a “comfort” letter or letters from the Company’s independent public accountants in customary form and covering matters of the type customarily covered by “comfort” letters;

(j) make available for inspection by any seller of such Registrable Securities covered by such registration statement, by any managing underwriter or underwriters participating in any disposition to be effected pursuant to such registration statement and by any attorney, accountant or other agent retained by any such seller or any such managing underwriter(s), all pertinent financial and other records, pertinent corporate documents and properties of the Company, and cause all of the Company’s officers, directors and employees to supply all information reasonably requested by any such seller, underwriter, attorney, accountant or agent in connection with such registration statement or underwritten offering;

(k) notify counsel (selected pursuant to Section 2.3.3 hereof) for the Holders of Registrable Securities included in such registration statement and the managing underwriter or agent, immediately, and confirm the notice in writing (i) when the registration statement, or any post-effective amendment to the registration statement, shall have become effective, or any supplement to the prospectus or any amendment to the prospectus shall have been filed, (ii) of the receipt of any comments from the Commission, (iii) of any request of the Commission to amend the registration statement or amend or supplement the prospectus or for additional information, and (iv) of the issuance by the Commission of any stop order suspending the effectiveness of the registration statement or of any order preventing or suspending the use of any preliminary prospectus, or of the suspension of the qualification of the registration statement for offering or sale in any jurisdiction, or of the institution or threatening of any proceedings for any of such purposes;

(l) use its reasonable best efforts to prevent the issuance of any stop order suspending the effectiveness of the registration statement or of any order preventing or suspending the use of any preliminary prospectus and, if any such order is issued, to obtain the withdrawal of any such order as soon as practicable;

(m) if requested by the managing underwriter or agent or any Holder of Registrable Securities covered by the registration statement, incorporate in a prospectus supplement or post-effective amendment such information as the managing underwriter or agent or such Holder reasonably requests to be included therein, including, with respect to the number of Registrable Securities being sold by such Holder to such underwriter or agent, the purchase price being paid therefor by such underwriter or agent and with respect to any other terms of the underwritten offering of the Registrable Securities to be sold in such offering; and make all required filings of such prospectus supplement or post-effective amendment as soon as practicable after being notified of the matters incorporated in such prospectus supplement or post-effective amendment;

(n) cooperate with the Holders of Registrable Securities covered by the registration statement and the managing underwriter or agent, if any, to facilitate the timely preparation and delivery of certificates (not bearing any restrictive legends) representing securities to be sold under the registration statement, and enable such securities to be in such denominations and registered in such names as the managing underwriter or agent, if any, or such Holders may request;

(o) obtain for delivery to the Holders of Registrable Securities being registered and to the underwriter or agent an opinion or opinions from counsel for the Company in customary form and in form, substance and scope reasonably satisfactory to such Holders, underwriters or agents and their counsel;

(p) cooperate with each seller of Registrable Securities and each underwriter or agent participating in the disposition of such Registrable Securities and their respective counsel in connection with any filings required to be made with the FINRA;

(q) use its reasonable best efforts to make available the executive officers of the Company to participate with the Holders of Registrable Securities and any underwriters in any “road shows” that may be reasonably requested by the Holders in connection with distribution of the Registrable Securities;

(r) cooperate with the Participating Investors and with the managing underwriter or agent, if any, to facilitate any Charitable Gifting Event and to prepare and file with the Commission such amendments and supplements to such registration statement and the prospectus used in connection therewith as may be necessary to permit any such recipient Charitable Organization to sell in any Public Offering if it so elects.

2.3.4. Selection of Underwriters and Counsel. The underwriters and legal counsel to be retained by the Company in connection with any registration or Public Offering shall be selected by the Board; provided that, in the case of a registration

pursuant to, or a Public Offering following a request therefor under Section 2.1.1, such underwriters and counsel shall be reasonably acceptable to the Participating Investors. In connection with any registration of Registrable Securities pursuant to Sections 2.1 and 2.2 hereof, the Participating Investors may select one counsel (plus counsel in each additional jurisdiction applicable to such Participating Investors or the Company) to represent all Holders of Registrable Securities covered by such registration.

2.3.5. Lock-Up. If any registration pursuant to Section 2.1 of this Agreement shall be in connection with an underwritten Public Offering and if requested by the managing underwriters, the Company and each Holder agrees not to effect any public sale or distribution of Ordinary Shares of the Company (or securities convertible into or exchangeable or exercisable for Ordinary Shares) (in each case, other than as part of such underwritten public offering and other than pursuant to a registration on Form S-4 or S-8), within 90 days (or such shorter period as the managing underwriters may require) after, the effective date of such registration (except as part of such registration).

2.3.6. Other Agreements. The Company covenants and agrees that, so long as any Person holds any Registrable Securities in respect of which any registration rights provided for in Section 2.1 of this Agreement remain in effect, the Company will not, directly or indirectly, grant to any Person or agree to or otherwise become obligated in respect of rights of registration in the nature or substantially in the nature of those set forth in Section 2.1 or 2.2 of this Agreement that would have priority over the Registrable Securities with respect to the inclusion of such securities in any registration.

2.4. Indemnification and Contribution.

2.4.1. Indemnities of the Company. In the event of any registration of any Registrable Securities or other debt or equity securities of the Company or any of its subsidiaries under the Securities Act pursuant to this Section 2 or otherwise, and in connection with any registration statement or any other disclosure document produced by or on behalf of the Company or any of its subsidiaries including reports required and other documents filed under the Exchange Act, and other documents pursuant to which any debt or equity securities of the Company or any of its subsidiaries are sold (whether or not for the account of the Company or its subsidiaries), the Company will, and hereby does, and will cause each of its subsidiaries, jointly and severally, to indemnify and hold harmless each holder of Registrable Securities, any Person who is or might be deemed to be a controlling Person of the Company or any of its subsidiaries within the meaning of Section 15 of the Securities Act or Section 20 of the Exchange Act, their respective direct and indirect partners, advisory board members, directors, officers, trustees, members and shareholders, and each other Person, if any, who controls any such holder or any such controlling Person within the meaning of Section 15 of the Securities Act or Section 20 of the Exchange Act (each such Person being referred to herein as a “Covered Person”), against any losses, claims, damages or liabilities (or actions or proceedings in respect thereof), joint or several, to which such Covered Person may be or become subject under the Securities Act, the Exchange Act, any other securities or other law of any jurisdiction, the common law or otherwise, insofar as such losses, claims, damages or liabilities (or actions or proceedings in respect thereof) arise

out of or are based upon (i) any untrue statement or alleged untrue statement of any material fact contained or incorporated by reference in any registration statement under the Securities Act, any preliminary prospectus or final prospectus included therein, or any related summary prospectus, or any amendment or supplement thereto, or any document incorporated by reference therein, or any other such disclosure document (including reports and other documents filed under the Exchange Act and any document incorporated by reference therein) or other document or report, (ii) any omission or alleged omission to state therein a material fact required to be stated therein or necessary to make the statements therein not misleading or (iii) any violation or alleged violation by the Company or any of its subsidiaries of any federal, state, foreign or common law rule or regulation applicable to the Company or any of its subsidiaries and relating to action or inaction in connection with any such registration, disclosure document or other document or report, and will reimburse such Covered Person for any legal or any other expenses incurred by it in connection with investigating or defending any such loss, claim, damage, liability, action or proceeding; provided, however, that neither the Company nor any of its subsidiaries shall be liable to any Covered Person in any such case to the extent that any such loss, claim, damage, liability, action or proceeding arises out of or is based upon an untrue statement or alleged untrue statement or omission or alleged omission made in such registration statement, any such preliminary prospectus, final prospectus, summary prospectus, amendment or supplement, incorporated document or other such disclosure document or other document or report, in reliance upon and in conformity with written information furnished to the Company or to any of its subsidiaries through an instrument duly executed by such Covered Person specifically stating that it is for use in the preparation thereof. The indemnities of the Company and of its subsidiaries contained in this Section 2.4.1 shall remain in full force and effect regardless of any investigation made by or on behalf of such Covered Person and shall survive any transfer of securities or any termination of this Agreement.

2.4.2. Indemnities to the Company. Subject to Section 2.4.4, the Company and any of its subsidiaries may require, as a condition to including any securities in any registration statement filed pursuant to this Section 2, that the Company and any of its subsidiaries shall have received an undertaking satisfactory to it from the prospective seller of such securities, severally and not jointly, to indemnify and hold harmless the Company and any of its subsidiaries, each director of the Company or any of its subsidiaries, each officer of the Company or any of its subsidiaries who shall sign such registration statement and each other Person (other than such seller), if any, who controls the Company and any of its subsidiaries within the meaning of Section 15 of the Securities Act or Section 20 of the Exchange Act and each other prospective seller of such securities with respect to any statement in or omission from such registration statement, any preliminary prospectus, final prospectus or summary prospectus included therein, or any amendment or supplement thereto, or any other disclosure document (including reports and other documents filed under the Exchange Act or any document incorporated therein) or other document or report, if such statement or omission was made in reliance upon and in conformity with written information furnished to the Company or any of its subsidiaries through an instrument executed by such seller specifically stating that it is for use in the preparation of such registration

statement, preliminary prospectus, final prospectus, summary prospectus, amendment or supplement, incorporated document or other document or report. Such indemnity shall remain in full force and effect regardless of any investigation made by or on behalf of the Company, any of its subsidiaries or any such director, officer or controlling Person and shall survive any transfer of securities or any termination of this Agreement.

2.4.3. Contribution. If the indemnification provided for in Sections 2.4.1 or 2.4.2 hereof is unavailable to a party that would have been entitled to indemnification pursuant to the foregoing provisions of this Section 2.4 (an “Indemnitee”) in respect of any losses, claims, damages or liabilities (or actions or proceedings in respect thereof) referred to therein, then each party that would have been an indemnifying party thereunder shall, subject to Section 2.4.4 and in lieu of indemnifying such Indemnitee, contribute to the amount paid or payable by such Indemnitee as a result of such losses, claims, damages or liabilities (or actions or proceedings in respect thereof) in such proportion as is appropriate to reflect the relative fault of such indemnifying party on the one hand and such Indemnitee on the other in connection with the statements or omissions which resulted in such losses, claims, damages or liabilities (or actions or proceedings in respect thereof). The relative fault shall be determined by reference to, among other things, whether the untrue or alleged untrue statement of a material fact or the omission or alleged omission to state a material fact relates to information supplied by such indemnifying party or such Indemnitee and the parties’ relative intent, knowledge, access to information and opportunity to correct or prevent such statement or omission. The parties agree that it would not be just or equitable if contribution pursuant to this Section 2.4.3 were determined by pro rata allocation or by any other method of allocation which does not take account of the equitable considerations referred to in the preceding sentence. The amount paid or payable by a contributing party as a result of the losses, claims, damages or liabilities (or actions or proceedings in respect thereof) referred to above in this Section 2.4.3 shall include any legal or other expenses reasonably incurred by such Indemnitee in connection with investigating or defending any such action or claim. No Person guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of the Securities Act) shall be entitled to contribution from any Person who was not guilty of such fraudulent misrepresentation.

2.4.4. Limitation on Liability of Holders of Registrable Securities. The liability of each holder of Registrable Securities in respect of any indemnification or contribution obligation of such holder arising under this Section 2.4 shall not in any event exceed an aggregate amount equal to the net proceeds to such holder (after deduction of all underwriters’ discounts and commissions) from the disposition of the Registrable Securities disposed of by such holder pursuant to such registration.

2.4.5. Indemnification Procedures. Promptly after receipt by an Indemnitee of written notice of the commencement of any action or proceeding with respect to which a claim for indemnification may be made pursuant to this Section 2.4, such Indemnitee will, if a claim in respect thereof is to be made against an indemnifying party, give written notice to the latter of the commencement of such action or proceeding; provided that the failure of the Indemnitee to give notice as provided herein shall not relieve the

indemnifying party of its obligations under this Section 2.4, except to the extent that the indemnifying party loses substantive legal rights by such failure to give notice. In case any such action or proceeding is brought against an Indemnitee, the indemnifying party will be entitled to participate in and to assume the defense thereof (at its expense), jointly with any other indemnifying party similarly notified to the extent that it may wish, with counsel reasonably satisfactory to such Indemnitee, and after notice from the indemnifying party to such Indemnitee of its election so to assume the defense thereof, the indemnifying party will not be liable to such Indemnitee for any legal or other expenses subsequently incurred by the latter in connection with the defense thereof other than reasonable costs of investigation and shall have no liability for any settlement made by the Indemnitee without the consent of the indemnifying party, such consent not to be unreasonably withheld. Notwithstanding the foregoing, if in such Indemnitee’s reasonable judgment a conflict of interest between such Indemnitee and the indemnifying parties may exist in respect of such action or proceeding or the indemnifying party does not assume the defense of any such action or proceeding within a reasonable time after notice of commencement, the Indemnitee shall have the right to assume or continue its own defense and the indemnifying party shall be liable for any reasonable expenses therefor, but in no event will bear the expenses for more than one firm of counsel for all Indemnitees in each jurisdiction, unless there is a conflict of interest among Indemnitees, in which case the indemnifying party shall be liable for the reasonable expenses of additional counsel. No indemnifying party will settle any action or proceeding or consent to the entry of any judgment without the prior written consent of the Indemnitee, unless such settlement or judgment (i) includes as an unconditional term thereof the giving by the claimant or plaintiff of a release to such Indemnitee from all liability in respect of such action or proceeding and (ii) does not involve an admission of fault, the imposition of equitable remedies or the imposition of any obligations on such Indemnitee and does not otherwise adversely affect such Indemnitee, other than as a result of the imposition of financial obligations for which such Indemnitee will be indemnified hereunder.

The parties shall have all remedies available at law, in equity or otherwise in the event of any breach or violation of this Agreement or any default hereunder. The parties acknowledge and agree that in the event of any breach of this Agreement, in addition to any other remedies which may be available, each of the parties hereto shall be entitled to specific performance of the obligations of the other parties hereto and, in addition, to such other equitable remedies (including preliminary or temporary relief) as may be appropriate in the circumstances.

4.1. Oral Modifications. This Agreement may not be orally amended, modified, extended or terminated, nor shall any oral waiver of any of its terms be effective.

4.2. Written Modifications. This Agreement may be amended, modified, extended or terminated, and the provisions hereof may be waived, only by an agreement in writing signed by the Company and the Investors holding a majority of Registrable Securities held by all Investors.

Each such amendment shall be binding upon each party hereto and each Holder of Registrable Securities. In addition, each party hereto and each Holder of Registrable Securities may waive any right hereunder by an instrument in writing signed by such party or holder.

4.3. Effect of Termination. No termination under this Agreement shall relieve any Person of liability for breach prior to termination. In the event this Agreement is terminated, each Investor shall retain the indemnification rights pursuant to Section 2.4 hereof with respect to any matter that (i) may be an indemnified liability thereunder and (ii) occurred prior to such termination.

For purposes of this Agreement:

5.1. Certain Matters of Construction. In addition to the definitions referred to or set forth below in this Section 5:

(i) The words “hereof’, “herein”, “hereunder” and words of similar import shall refer to this Agreement as a whole and not to any particular Section or provision of this Agreement, and reference to a particular Section of this Agreement shall include all subsections thereof;

(ii) The word “including” shall mean including, without limitation;

(iii) Definitions shall be equally applicable to both nouns and verbs and the singular and plural forms of the terms defined; and

(iv) The masculine, feminine and neuter genders shall each include the other.

5.2. Definitions. The following terms shall have the following meanings:

“Affiliate” shall mean, with respect to any specified Person, (a) any other Person which directly or indirectly through one or more intermediaries controls, or is controlled by, or is under common control with, such specified Person (for the purposes of this definition “control” (including, with correlative meanings, the terms “controlling,” “controlled by” and “under common control with”), as used with respect to any Person, means the possession, directly or indirectly, of the power to direct or cause the direction of the management or policies of such Person, whether through the ownership of voting securities, by agreement or otherwise); provided, however, that neither the Company nor any of its subsidiaries shall be deemed an Affiliate of any of the Investors (and vice versa), (b) if such specified Person is an investment fund, any other investment fund the primary investment advisor to which is the primary investment advisor to such specified Person or an Affiliate thereof and (c) if such specified Person is a natural Person, any Family Member of such natural Person.

“Agreement” shall have the meaning set forth in the Preamble.

“Board” shall mean the board of directors of the Company.

“business day” shall mean any day that is not a Saturday, a Sunday or other day on which banks are required or authorized by law to be closed in the City of New York.

“Charitable Gifting Event” means any transfer by a holder of Registrable Securities, or any subsequent transfer by such holder’s members, partners or other employees, in connection with a bona fide gift to any Charitable Organization made on the date of, but prior to, the execution of the underwriting agreement entered into in connection with any underwritten Public Offering.

“Charitable Organization” shall mean a charitable organization as described by Section 501(c)(3) of the Internal Revenue Code of 1986, as in effect from time to time.

“Commission” shall mean the Securities and Exchange Commission.

“Company” shall have the meaning set forth in the Preamble.

“Covered Person” shall have the meaning set forth in Section 2.4.1.

“Exchange Act” shall mean the Securities Exchange Act of 1934, as in effect from time to time.

“Family Member” shall mean, with respect to any natural Person, (i) any lineal descendant or ancestor or sibling (by birth or adoption) of such natural Person, (ii) any spouse or former spouse of any of the foregoing, (iii) any legal representative or estate of any of the foregoing, (iv) any trust maintained for the benefit of any of the foregoing and (v) any corporation, private charitable foundation or other organization controlled by any of the foregoing.

“FINRA” shall mean the Financial Industry Regulatory Authority.

“Holders” shall mean the holders of Registrable Securities under this Agreement and, with respect to any Investor, any shareholder, partner or manager of such Investor who receives Registrable Securities from such Investor.

“Indemnitee” shall have the meaning set forth in Section 2.4.3.

“IPO” shall have the meaning set forth in the recitals.

“Investors” shall have the meaning set forth in the Preamble.

“Lock-Up Agreement” shall mean a customary lock-up agreement with the underwriter(s) of a Public Offering restricting the Person’s right to transfer any Ordinary Shares or any securities convertible into or exercisable or exchangeable for such Ordinary Shares or (b) enter into any swap or other arrangement that transfers to another any of the economic consequences of ownership of Ordinary Shares.

“Ordinary Shares” shall mean the ordinary shares, $0.01 par value per share, of the Company.

“Parity Shares” shall have the meaning set forth in Section 2.3.1.

“Participating Investors” shall mean the Investors holding the majority of the Registrable Securities requested to be included in any registration or underwritten Public Offering, as applicable.”

“Permitted Transferee” shall mean, with respect to any Investor, any Affiliate of such Investor, to the extent such Person agrees in writing to be bound by the terms of this Agreement.

“Person” shall mean any individual, partnership, corporation, company, association, trust, joint venture, limited liability company, unincorporated organization, entity or division, or any government, governmental department or agency or political subdivision thereof.

“Pro Rata Portion” shall mean for purposes of Section 2.3, with respect to each holder of Registrable Securities or Parity Shares requesting that such shares be registered in such registration statement, a number of such shares equal to the aggregate number Ordinary Shares requested to be registered in such registration (excluding any shares to be registered for the account of the Company) multiplied by a fraction, the numerator of which is the aggregate number of Registrable Securities and Parity Shares held by such holder, and the denominator of which is the aggregate number of Registrable Securities and Parity Shares held by all holders requesting that their Registrable Securities or Parity Shares be registered in such registration.

“Public Offering” shall mean a public offering and sale of Ordinary Shares for cash pursuant to an effective registration statement under the Securities Act.

“Registrable Securities” shall mean (a) all Ordinary Shares and (b) all securities directly or indirectly issued or issuable with respect to such Ordinary Shares by way of stock dividend or stock split or in connection with a combination of shares, recapitalization, merger, consolidation or other reorganization, in each case constituting Shares. As to any particular Registrable Securities, such shares shall cease to be Registrable Securities when (i) a registration statement with respect to the sale of such securities shall have become effective under the Securities Act and such securities shall have been disposed of in accordance with such registration statement, (ii) such securities have been Transferred pursuant to Rule 144 or Rule 145, (iii) the aggregate number of such securities held by the applicable Holder and its Affiliates is less than the number that would subject the distribution thereof to any volume limitation or other restriction on transfer under Rule 144 and such holder is able to immediately distribute such securities publicly without any restrictions on transfer without application of paragraphs (c), (e) (f) and (h) of Rule 144) (iv) such securities shall have been otherwise transferred to a Person and subsequent disposition of them shall not require registration of them under the Securities Act and such securities may be distributed without volume limitation or other restrictions on transfer under Rule 144 or Rule 145 (including without application of paragraphs (c), (e) (f) and (h) of Rule 144), or (v) such securities shall have ceased to be outstanding.

“Registration Expenses” means any and all expenses incident to performance of or compliance with Section 2 of this Agreement (other than underwriting discounts and commissions paid to underwriters and transfer taxes, if any), including (a) all Commission, securities exchange and FINRA registration and filing fees, (b) all fees and expenses of complying with securities or blue sky laws (including reasonable fees and disbursements of counsel for the underwriters in connection with blue sky qualifications of the Registrable Securities), (c) all printing, messenger and delivery expenses, (d) all fees and expenses incurred in connection with the listing of the Registrable Securities on any securities exchange and obtaining FINRA clearance pursuant to Section 2.3.2(g) and all rating agency fees, (e) the fees and disbursements of counsel for the Company and of its independent public accountants, including the expenses of any special audits and/or “cold comfort” letters required by or incident to such performance and compliance, (f) the reasonable fees and disbursements of one counsel (plus counsel in each additional jurisdiction applicable to such Holder or the Company) for the Holders selected pursuant to the terms of Section 2 and one counsel (plus counsel in each additional jurisdiction applicable to such Holder or the Company) for certain Holders selected pursuant to the second proviso of Section 2.3.3, if applicable, (g) any fees and disbursements customarily paid by the issuers of securities, and (h) expenses incurred in connection with any road show (including the reasonable out-of-pocket expenses of the Holders).

“Rule 144” shall mean Rule 144 under the Securities Act (or any successor Rule).

“Rule 145” shall mean Rule 145 under the Securities Act (or any successor Rule).

“Rule 145 Transaction” shall mean a registration on Form S-4 (or any successor Form) pursuant to Rule 145.

“Sale” shall mean a Transfer for value and the terms “Sell” and “Sold” shall have correlative meanings.

“Securities Act” shall mean the Securities Act of 1933, as in effect from time to time.

“Shares” shall mean all Ordinary Shares held by an Investor, whenever issued.

“Transfer” shall mean any sale, pledge, assignment, encumbrance or other transfer or disposition of any Shares to any other Person, whether directly, indirectly, voluntarily, involuntarily, by operation of law, pursuant to judicial process or otherwise.

6.1. Authority: Effect. Each party hereto represents and warrants to and agrees with each other party that the execution and delivery of this Agreement and the consummation of the transactions contemplated hereby have been duly authorized on behalf of such party and do not violate any agreement or other instrument applicable to such party or by which its assets are bound. This Agreement does not, and shall not be construed to, give rise to the creation of a partnership among any of the parties hereto, or to constitute any of such parties members of a joint venture or other association.

6.2. Notices. Any notices and other communications required or permitted in this Agreement shall be effective if in writing and (a) delivered personally, (b) sent by facsimile, or (c) sent by overnight courier, in each case, addressed as follows:

If to the Company, to:

Trinseo S.A.

1000 Chesterbrook Boulevard

Suite 300

Berwyn, PA 19312

Attention:     Curtis S. Shaw,

                      Executive Vice President, General Counsel and Corporate Secretary

Facsimile:     [     ]

E-mail:           ***@***

With a copy to:

Ropes & Gray LLP

800 Boylston Street

Boston, MA 02199 Attention: Craig E. Marcus

E-mail: ***@***

If to the Investor, to:

Bain Capital Everest Manager Holding SCA

9A, Parc d’Activité Syrdall

L-5365 Munsbach

Grand Duché de Luxembourg

Attn: Michel Plantevin

E-mail: ***@***

With a copy to:

Ropes & Gray LLP

800 Boylston Street

Boston, MA 02199

Attention: Craig E. Marcus

E-mail: ***@***

Notice to the holder of record of any shares of capital stock shall be deemed to be notice to the holder of such shares for all purposes hereof.

Unless otherwise specified herein, such notices or other communications shall be deemed effective (a) on the date received, if personally delivered, (b) on the date received if delivered by facsimile on a business day, or if not delivered on a business day, on the first business day thereafter and (b) two business days after being sent by overnight courier. Each of the parties hereto shall be entitled to specify a different address by giving notice as aforesaid to each of the other parties hereto.

6.3. Binding Effect, Etc. This Agreement constitutes the entire agreement of the parties with respect to its subject matter, supersede all prior or contemporaneous oral or written agreements or discussions with respect to such subject matter, and shall be binding upon and inure to the benefit of the parties hereto and thereto and their respective heirs, representatives, successors and permitted assigns. Except as otherwise expressly provided herein, no Investor or other party hereto may assign any of its respective rights or delegate any of its respective obligations under this Agreement without the prior written consent of the other parties hereto, and any attempted assignment or delegation in violation of the foregoing shall be null and void.

6.4. Successors and Assigns. This Agreement shall be binding upon and inure to the benefit of and be enforceable by the parties hereto and their respective successors and assigns; provided that the provisions of this Agreement which are for the benefit of Investors are only assignable to, and enforceable by, a Permitted Transferee.

6.5. Descriptive Heading. The descriptive headings of this Agreement are for convenience of reference only, are not to be considered a part hereof and shall not be construed to define or limit any of the terms or provisions hereof.

6.6. Counterparts. This Agreement may be executed in multiple counterparts, each of which shall be deemed an original, but all of which taken together shall constitute one instrument.

6.7. Severability. In the event that any provision hereof would, under applicable law, be invalid or unenforceable in any respect, such provision shall be construed by modifying or limiting it so as to be valid and enforceable to the maximum extent compatible with, and possible under, applicable law. The provisions hereof are severable, and in the event any provision hereof should be held invalid or unenforceable in any respect, it shall not invalidate, render unenforceable or otherwise affect any other provision hereof.

6.8. No Recourse. Notwithstanding anything that may be expressed or implied in this Agreement, the Company and each Investor covenant, agree and acknowledge that no recourse under this Agreement or any documents or instruments delivered in connection with this Agreement shall be had against any current or future director, officer, employee, general or limited partner or member of any Investor or of any Affiliate or assignee thereof, as such, whether by the enforcement of any assessment or by any legal or equitable proceeding, or by virtue of any statute, regulation or other applicable law, it being expressly agreed and acknowledged that no personal liability whatsoever shall attach to, be imposed on or otherwise be incurred by any current or future officer, agent or employee of any Investor or any current or future member of any Investor or any current or future director, officer, employee, partner or member of any Investor or of any Affiliate or assignee thereof, as such, for any obligation of any Investor under this Agreement or any documents or instruments delivered in connection with this Agreement for any claim based on, in respect of or by reason of such obligations or their creation.

7.1. Governing Law. This Agreement and all claims arising out of or based upon this Agreement or relating to the subject matter hereof shall be governed by and construed in accordance with the domestic substantive laws of the State of Delaware without giving effect to any choice or conflict of laws provision or rule that would cause the application of the domestic substantive laws of any other jurisdiction.

7.2. Consent to Jurisdiction. Each party to this Agreement, by its execution hereof, (a) hereby irrevocably submits to the exclusive jurisdiction of the state and federal courts sitting in the State of Delaware for the purpose of any action, claim, cause of action or suit (in contract, tort or otherwise), inquiry, proceeding or investigation arising out of or based upon this Agreement or relating to the subject matter hereof, (b) hereby waives to the extent not prohibited by applicable law, and agrees not to assert, and agrees not to allow any of its subsidiaries to assert, by way of motion, as a defense or otherwise, in any such action, any claim that it is not subject personally to the jurisdiction of the above-named courts, that its property is exempt or immune from attachment or execution, that any such proceeding brought in one of the above-named courts is improper, or that this Agreement or the subject matter hereof or thereof may not be enforced in or by such court and (c) hereby agrees not to commence or maintain any action, claim, cause of action or suit (in contract, tort or otherwise), inquiry, proceeding or investigation arising out of or based upon this Agreement or relating to the subject matter hereof or thereof other than before one of the above-named courts nor to make any motion or take any other action seeking or intending to cause the transfer or removal of any such action, claim, cause of action or suit (in contract, tort or otherwise), inquiry, proceeding or investigation to any court other than one of the above-named courts whether on the grounds of inconvenient forum or otherwise. Notwithstanding the foregoing, to the extent that any party hereto is or becomes a party in any litigation in connection with which it may assert indemnification rights set forth in this agreement, the court in which such litigation is being heard shall be deemed to be included in clause (a) above. Notwithstanding the foregoing, any party to this Agreement may commence and maintain an action to enforce a judgment of any of the above-named courts in any court of competent jurisdiction. Each party hereto hereby consents to service of process in any such proceeding in any manner permitted by Delaware law, and agrees that service of process by registered or certified mail, return receipt requested, at its address specified pursuant to Section 8.2 hereof is reasonably calculated to give actual notice.

7.3. WAIVER OF JURY TRIAL. TO THE EXTENT NOT PROHIBITED BY APPLICABLE LAW WHICH CANNOT BE WAIVED, EACH PARTY HERETO HEREBY WAIVES AND COVENANTS THAT IT WILL NOT ASSERT (WHETHER AS PLAINTIFF, DEFENDANT OR OTHERWISE) ANY RIGHT TO TRIAL BY JURY IN ANY FORUM IN RESPECT OF ANY ISSUE OR ACTION, CLAIM, CAUSE OF ACTION OR SUIT (IN CONTRACT, TORT OR OTHERWISE), INQUIRY, PROCEEDING OR INVESTIGATION ARISING OUT OF OR BASED UPON THIS AGREEMENT OR THE SUBJECT MATTER HEREOF OR IN ANY WAY CONNECTED WITH OR RELATED OR INCIDENTAL TO THE TRANSACTIONS CONTEMPLATED HEREBY, IN EACH CASE WHETHER NOW EXISTING OR HEREAFTER ARISING. EACH PARTY HERETO ACKNOWLEDGES THAT IT HAS BEEN INFORMED BY THE OTHER PARTIES HERETO THAT THIS SECTION 7.3 CONSTITUTES A MATERIAL INDUCEMENT UPON WHICH THEY ARE RELYING AND WILL RELY IN ENTERING INTO THIS AGREEMENT. ANY PARTY HERETO MAY FILE AN ORIGINAL COUNTERPART OR A COPY OF THIS SECTION 7.3 WITH ANY COURT AS WRITTEN EVIDENCE OF THE CONSENT OF EACH SUCH PARTY TO THE WAIVER OF ITS RIGHT TO TRIAL BY JURY.

7.4. Exercise of Rights and Remedies. No delay of or omission in the exercise of any right, power or remedy accruing to any party as a result of any breach or default by any other party under this Agreement shall impair any such right, power or remedy, nor shall it be construed as a waiver of or acquiescence in any such breach or default, or of any similar breach or default occurring later; nor shall any such delay, omission nor waiver of any single breach or default be deemed a waiver of any other breach or default occurring before or after that waiver.

[Signature pages follow]

IN WITNESS WHEREOF, each of the undersigned has duly executed this Agreement (or caused this Agreement to be executed on its behalf by its officer or representative thereunto duly authorized) under seal as of the date first above written.