* * * *

Exhibit 10.1

Execution Copy

March 31, 2009

Thomas Joyce

545 Washington Boulevard

Jersey City, NJ 07310

Dear Tom:

This Letter Agreement sets forth the terms and conditions of your continued employment with Knight Capital Group, Inc. (the “Company”), and amends and restates the Letter Agreement we entered into on December 24, 2008. Capitalized terms not otherwise defined shall have the meanings set forth in paragraph 7(d) below.

(i) the Accrued Obligations;

(ii) vesting (and if applicable, delivery) of the Shares underlying any unvested Bonus Share award (including with respect to awards granted in respect of annual bonuses for periods that commenced prior to the Effective Date, including your calendar-year 2008 Bonus Share award) and vesting and exercisability of any stock options granted to you in respect of any annual bonus award in respect of a period commencing prior to the Effective Date, 100% of which shall vest and, if applicable, become immediately exercisable or be delivered within 15 days following the Release Date (as defined below) (the “Vesting Bonus Shares”);

(iii) vesting (and, if applicable, exercisability or delivery) of (A) the unvested portion of the First Tranche, 50% of which shall vest and be delivered within 15 days following the Release Date (such 50%, the “Initial Vesting First Tranche”), and 50% of which shall vest and be delivered on the earlier of the date that is six months following such termination or March 15 of the year following the year of such termination (provided that such vesting and delivery shall be conditional upon, and in no event occur until, a determination that the performance criteria relating to pre-tax income as set forth in paragraph 5(c) has been satisfied) (such 50%, the “Delayed Vesting First Tranche”), and (B) any time-based vesting awards that have been granted to you in respect of periods commencing before the Effective Date (other than any Bonus Share awards), 50% of which shall vest (and, if applicable, become exercisable or be delivered) within 15 days following the Release Date (such 50%, the “Initial Vesting Time-Based Awards”) and 50% of which shall vest (and, if applicable become exercisable or be delivered) on the earlier of the date that is six months following such termination or March 15 of the year following the year of such termination (such 50% the “Delayed Vesting Time-Based Awards”);

(iv) a cash payment equal to $5 million, 50% of which is payable within 15 days following the Release Date (such 50%, the “Initial Cash Payment” and together with the Initial Vesting First Tranche and the Initial Vesting Time Based Awards, the “Initial Awards and Payments”), and 50% of which is payable on the earlier of the date that is six months following such termination or March 15 of the year following the year of such termination (such 50%, the “Delayed Cash Payment” and together with the Delayed Vesting First Tranche and the Delayed Vesting Time-Based Awards, the “Delayed Awards and Payments”);

(v) payment of the Annual Bonus in respect of the year in which such termination occurs at the time such Annual Bonus would otherwise have been paid had your employment not

terminated (determined based on actual performance consistent with this Letter Agreement), provided that the amount shall be prorated to reflect the portion of the year that you were actually employed and shall be paid all in cash (the “Pro-Rata Bonus”);

(vi) to the extent not already paid, payment of the Annual Bonus (to the extent not determined prior to the date of termination, determined based on actual performance consistent with this Letter Agreement) in respect of the year immediately prior to the year in which such termination occurs at the time such Annual Bonus would otherwise have been paid had your employment not terminated, provided that the amount shall be paid all in cash (the “Prior Year Bonus”); and

(vii) payment of your premiums for continued health coverage under “COBRA” during the one year period following termination of your employment (the “Benefits Continuation Period”), provided and to the extent that you are eligible for and timely and properly elect to receive such COBRA coverage, provided further that in the event you cease COBRA coverage, the Company shall not be obligated to pay you any future installments of the Health Payment (as defined below). The Company shall pay you in advance an amount equal to three times the monthly premium amount payable by you for such COBRA coverage (the “Health Payment”), no later than the first date of the month following your date of termination and on the first business day of each of the third, sixth and ninth months thereafter. The Health Payments are intended to qualify for the exception from deferred compensation as a medical benefit provided in accordance with the requirements of Treas. Reg. §1.409A-1(b)(9)(v)(B). The Benefits Continuation Period shall be concurrent with and applied toward any coverage period required under COBRA.

Your right to the vesting/delivery and payments in respect of the Vesting Bonus Shares, the Initial Awards and Payments, the Delayed Awards and Payments, the Pro-Rata Bonus, and the Health Payments shall be conditional upon your execution of a release of all claims against the Company and its affiliates and representatives in the form attached as Exhibit A which shall be delivered to the Company within 21 days following your termination, and no such vesting/delivery or payments shall be made until the lapse of any period during which you may revoke the release (the date of which such release becomes irrevocable, the “Release Date”). Your right to the vesting/delivery and payments in respect of the Delayed Awards and Payments shall be conditional upon, during the six month period following termination of your employment, your not, directly or indirectly (including on behalf of another person), hiring or attempting to hire any person who is or was employed by the Company or its affiliates at any time after the date that is six months prior to the date of termination of your employment, or otherwise induce any such person to terminate his or her employment with the Company or its affiliates, and if you fail to abide by this covenant, you will forfeit your entitlement to the vesting/delivery or payment in respect of the Delayed Awards and Payments, and shall immediately return to the Company any Shares already delivered or payments already made in respect of the Vesting Bonus Shares, the Initial Awards and Payments and the Pro-Rata Bonus.

*    *    *    *

Please indicate your acceptance of our offer of employment on the terms and conditions outlined above by signing and returning to us one copy of this letter.

Exhibit A

RELEASE

I, Thomas Joyce, the undersigned, agree to accept the compensation, payments, benefits and other consideration provided for in paragraph 7(b) of the employment letter agreement between me and Knight Capital Group, Inc. (the “Company”) dated March 31, 2009 (the “Letter Agreement”) in full resolution and satisfaction of, and hereby IRREVOCABLY AND UNCONDITIONALLY RELEASE, REMISE AND FOREVER DISCHARGE the Company and the Releasees from any and all legally waiveable agreements, promises, liabilities, claims, demands, rights and entitlements of any kind whatsoever, in law or equity, whether known or unknown, asserted or unasserted, fixed or contingent, apparent or concealed, which I, my heirs, executors, administrators, successors or assigns ever had, now have or hereafter can, shall or may have for, upon, or by reason of any matter, cause or thing whatsoever existing, arising or occurring at any time on or prior to the date I execute this Release (“Claims”), including, without limitation, any and all claims arising out of or relating to my employment, compensation and benefits with the Company and/or the termination thereof, my status as a stockholder of the Company, and any and all contract claims, benefit claims, tort claims, fraud claims, claims under any employment agreement (and any predecessor agreement), commission claims, defamation claims, disparagement claims, or other personal injury claims, claims related to any bonus compensation, claims for accrued vacation pay, claims for wrongful discharge of any type, including, but not limited to, in violation of public policy, claims under any federal, state or municipal wage payment, discrimination or fair employment practices law, statute or regulation, and claims for costs, expenses and attorneys’ fees with respect thereto. THIS RELEASE AND WAIVER INCLUDES, WITHOUT LIMITATION, ANY AND ALL RIGHTS AND CLAIMS UNDER TITLE VII OF THE CIVIL RIGHTS ACT OF 1964, AS AMENDED, THE CIVIL RIGHTS ACT OF 1991, THE CIVIL RIGHTS ACT OF 1866 (42 U.S.C. 1981), THE EMPLOYEE RETIREMENT INCOME SECURITY ACT, AS AMENDED, THE AMERICANS WITH DISABILITIES ACT, THE FAMILY AND MEDICAL LEAVE ACT, THE AGE DISCRIMINATION IN EMPLOYMENT ACT, THE NEW JERSEY LAW AGAINST DISCRIMINATION, THE SARBANES-OXLEY ACT OF 2002, THE NEW JERSEY WAGE PAYMENT ACT, THE NEW JERSEY FAMILY LEAVE ACT, THE NEW JERSEY CONSCIENTIOUS EMPLOYEE PROTECTION ACT; and all other federal, state or local fair employment practices statutes, ordinances, regulations or constitutional provisions; provided, however, that nothing in this waiver and release shall affect, and this waiver and release expressly excludes any Claim relating to: (i) my rights under paragraph 7(b) of the Letter Agreement, (ii) my rights to tax gross-ups under paragraphs 6 and 10(b) of the Letter Agreement, (iii) any indemnification obligations to me under the Company’s by-laws, certificate of incorporation, Delaware law or by agreement, including as set forth in paragraph 10 of the Letter Agreement, (iv) my rights under any equity compensation awards or agreements or obligations under any pension plan or other benefit or deferred compensation plan, in each case to the extent not otherwise addressed in paragraph 7(b) of the Letter Agreement, all of which shall remain in effect in accordance with their terms, (v) obligations with respect to insurance coverage under any directors’ and officers’ liability insurance policies, and (vi) on facts or circumstances arising after the date hereof.

To the fullest extent permitted by law, I represent and affirm that: (i) I have not filed or caused to be filed on my behalf any claim for relief against the Company before any arbitral, administrative, regulatory, self-regulatory, judicial, legislative, or other body or agency, and, to the best of my knowledge and belief, no outstanding claims for relief have been filed or asserted against the Company on my behalf, whether in my name or on my behalf as part of a class, collective or representative action; and (ii) I have not reported any purported improper, unethical or illegal conduct or activities to any supervisor, manager, department head, Human Resources representative, agent or other representative of the Company, to any member of Knight’s legal or compliance departments, or to the Company’s Ethics Committee, and have no knowledge of any such improper, unethical or illegal conduct or activities.

For the purpose of implementing a full and complete release and discharge of claims, I expressly acknowledge that this Release is intended to include in its effect, without limitation, all the claims described in the first paragraph above, whether known or unknown, apparent or concealed, and that this Release contemplates the extinction of all such claims, including claims for attorney’s fees. I expressly waive any right to assert after the execution of this Release that any such claim, demand, obligation or cause of action has, through ignorance or oversight, been omitted from the scope of this Release.

For purposes of this Release, the terms “the Company and the Releasees” and “the Company or the Releasees”, include the Company, Knight Equity Markets, L.P., and any past, present and future direct and indirect parents, subsidiaries, affiliates, divisions, predecessors, successors, and assigns, and their past, present and future officers, directors, shareholders, representatives, employees, agents and attorneys, in their official and individual capacities, and all other related individuals and entities, jointly and individually, and this Release shall inure to the benefit of and be enforceable by all such entities and individuals and their successors and assigns.

I release all claims for events or omissions occurring prior to the date of this Release, except that nothing in this Release shall be construed to prevent me from filing or participating in a charge of discrimination filed with the Equal Employment Opportunity Commission (“EEOC”). However, by signing this Release, I waive the right to recover any monetary damages or attorneys’ fees from the Company in any claim or lawsuit brought by or through the EEOC.

I understand that I have a period of up to 21 days from my receipt of this Release to review and consider this Release. I further understand that once I have signed this Release, I may revoke it at any time during the 7 days following its execution by delivering a written notice of revocation to the Company, attention General Counsel. I further understand that if I fail to execute and return this Release to the Company, attention General Counsel, prior to the expiration of such 21 day period, or revoke my execution of the Release during such 7 day period, I will not be entitled to the compensation, payments, benefits and other consideration provided for in paragraph 7(b) of the Letter Agreement (other than the “Accrued Obligations”, as defined therein).

I ACKNOWLEDGE THAT I HAVE READ THIS

RELEASE AND I UNDERSTAND

AND ACCEPT ITS TERMS