FORM OF SAVINGS INSTITUTE SUPPLEMENTAL EXECUTIVE RETIREMENT PLAN

Exhibit 10.10

FORM OF

SAVINGS INSTITUTE

SUPPLEMENTAL EXECUTIVE RETIREMENT PLAN

Article 1

Description, Purpose and Definitions

1.1 Name. The name of this Plan is the “Savings Institute Supplemental Executive Retirement Plan.”

1.2 Purpose. The purpose of the Plan is to promote the recruitment and retention of high quality management personnel by providing an additional source of retirement income to supplement that available to Participants from other sources.

1.3 Definitions. For purposes of the Plan, the following words and phrases shall have the meanings indicated, unless the context clearly indicates otherwise.

“Accrued Liability Balance” means the amount equal to a Participant’s accrued benefit, which is or which should have been reflected as a liability on the Bank’s financial statements during the period beginning with the Effective Date of the Plan and ending on the Participant’s date of death or termination of employment without Cause; provided, however, that for the year in which the Participant dies or is terminated, such amount shall be adjusted upwards to reflect the accruals during the period since the Bank’s most recent financial statements.

“Administrator” means the Human Resources Committee of the Board of Directors of the Bank.

“Bank” is the Savings Institute, Willimantic, Connecticut.

“Cause” means termination of employment because of the Participant’s personal dishonesty, incompetence, willful misconduct, breach of fiduciary duty involving personal profit, intentional failure to perform stated duties, willful violation of any law, rule or regulation (other than traffic violations or similar infractions) or a final cease-and-desist order.

“Change in Control” means any one of the following events occurs (i) If the Bank and/or its parent holding company SI Bancorp, Inc. (the “MHC”) shall be a party to any merger or consolidation with another bank, corporation, association or business entity (“Resulting Entity”), and, following such merger or consolidation, the Bank’s representatives serving as directors of the Resulting Entity shall constitute one-half or fewer of such board of directors; or (ii) If the Bank and/or MHC shall sell, exchange or transfer all or substantially all of its assets to some other person. In addition, if the Bank, the MHC or Resulting Entity issues shares of its capital stock to any person other than the MHC or a Resulting Entity then the Bank may, at its option, either treat the event as a Change in Control and make the payments otherwise required in a Change in Control situation or amend this Agreement to provide both for such change in control events as are analogous to those described in (i) and (ii) above and which are customary for publicly-traded companies.

“Contingent Disability Trust” means a trust created for the benefit of a Participant in circumstances set forth in Section 3.4(E).

“Compensation” shall have the same meaning as under the Bank’s 401(k) Plan at the time the amount of a Participant’s benefit is being determined; provided, however, that Compensation shall be determined without regard to any limitation on the maximum dollar amount of compensation taken into account under the Bank’s 401(k) Plan pursuant to Internal Revenue Code Section 401(a) (17) or any similar provision of law.

“Disability” means a Participant’s inability to perform substantially all normal duties of a Participant, as determined by the Administrator in its sole discretion. As a condition to any benefits, the Bank may require the executive to submit to such physical or mental evaluations and tests, as the Administrator deems appropriate.

“Eligible Employee” means one of a select group of management and highly compensated employees of the Bank designated by the Administrator as a Participant in the Plan or identified in Appendix A as a Participant.

“Final Average Compensation” means a Participant’s average Compensation over the three most recently completed years preceding his termination of employment.

“Participant” means an Eligible Employee who has been selected by the Administrator to participate in the Plan or who is identified in Appendix A.

“Social Security Benefit” means the amount, as determined by the Administrator in its discretion and based upon the Participant’s estimated earnings history to the date of his termination of employment with the Bank, to which a Participant will be entitled under the old age provisions of the Social Security Act upon attainment of the normal Social Security retirement age.

“Year(s) of Service” means each twelve (12) month period during which the Executive is employed on a full-time basis by the Bank, beginning on the Executive’s date of hire.

Article 2

Eligibility

2.1 Selection of Participants. After the effective date, an Eligible Employee shall become a Participant in the Plan only upon his selection by the Administrator. The Administrator shall give each Participant written notice of the commencement of his participation in the Plan. The initial Participants as of the effective date are identified in Appendix A to the Plan.

2.2 Entitlement to Benefits. Except to the extent provided in Sections 3.3, 3.4 and 3.5, a Participant shall become entitled to receive a benefit under the Plan only if his employment with the Bank terminates for reasons other than Cause (i) after he has attained age

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65 or (ii) on a date when the sum of the Participant’s age and Years of Service total at least 80. Notwithstanding anything in this Plan to the contrary, no benefit shall be payable to a Participant whose employment is terminated for Cause.

Article 3

Supplemental Retirement Benefits

3.1 Basic Benefit. Subject to the succeeding provisions of this Article, a Participant shall be entitled to an annual benefit equal to 70% of his Final Average Compensation upon the earlier of the Participant’s termination of employment (other than for Cause) (i) at or after attaining age 65 or (ii) on a date when the sum of the Participant’s age and Years of Service totals at least 80. Such benefit shall be paid in accordance with the Participant’s election under Section 3.6 at the time specified in Section 3.7.

3.2 Other Retirement Income Reduction.

3.3 Early Retirement Benefit. If a Participant’s termination of employment occurs prior to a date when the Participant is eligible to receive a benefit determined under Section 3.1, the Participant’s benefit shall equal the benefit determined under Section 3.1 reduced by 2% for each point by which the sum of the Participant’s age and Years of Service is less than 80. Such benefit shall be paid in accordance with the Participant’s election under Section 3.6 at the time specified in Section 3.7.

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3.4 Death and Disability Benefits.

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3.5 Change in Control Benefit.

If a Participant terminates employment with the Bank following a Change in Control (other than for Cause), there shall be paid to the Participant the amount set forth for the Participant in Column C of Schedule A of this Plan in lieu of any other benefit payable under the Plan. The Bank shall pay the benefit under this Section 3.5 to the Participant in a lump sum within 30 days of the Participant’s termination of employment.

3.6 Form of Benefit.

Upon a Participant’s entitlement to a benefit under Sections 3.1 or 3.3, the Participant’s benefit shall be paid in the form of (i) a single life annuity with 15 annual payments guaranteed or (ii) a lump sum which is actuarially equivalent to the annuity form of payment in (i), as designated by the Participant on an election form designated by the Bank for such purpose.

A Participant while employed by the Bank may change the form in which his benefits shall be paid by filing a revised election indicating such change at least one (1) calendar year prior to the date payments are to commence. Such election shall be irrevocable beginning one (1) calendar year prior to the date payments are to commence. No changes in the form of benefit payment shall be permitted following a Participant’s termination of employment.

3.7 Time of Payment.

Benefit payments made to a Participant or beneficiary pursuant to Sections 3.1 or 3.3 shall commence in accordance with the Participant’s election not later than 60 days following the Participant’s termination of employment.

3.8 Payment in the Event of Incapacity or Minority. If the Administrator, in its discretion, determines that any person entitled to receive any payment under this Plan is physically, mentally or legally incapable of receiving or acknowledging receipt of payment, and no legal representative has been appointed for such person, the Administrator in its discretion may (but shall not be required to) cause any sum otherwise payable to such person to be paid to such one or more as may be chosen by the Administrator from among the following: the institution maintaining such person, such person’s spouse, children, parents or other relatives by blood or marriage, a custodian under any applicable Uniform Transfers to Minors Act or any other person determined by the Administrator to have incurred expense for such person. The

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Administrator’s payment based upon its good faith determination of the incapacity of the person otherwise entitled to payments under this Plan and the existence of any other person specified above shall be conclusive and binding on all persons. Any such payment shall be a complete discharge of the liabilities of the Bank under this Plan to the extent of such payment.

Article 4

Source of Benefits

4.1 Employer Funds. This Plan is unfunded, and all benefits payable to Participants and beneficiaries shall be payable solely from the general assets of the Bank. No Participant shall be required or permitted to make any contribution to the Plan.

4.2 Trust Fund. The Bank may establish a trust from which part or all of the benefits under the Plan are to be paid. If a trust is established, all of the principal and income of such trust shall remain subject to the claims of the Bank’s creditors until applied to the payment of benefits.

4.3 Participant’s Right to Funds. This Plan constitutes a mere promise by the Bank to make benefit payments in the future. Beneficial ownership of any assets, whether cash or investments, that the Bank may earmark or place in trust to pay the Participants’ benefits under this Plan shall at all times remain in the Bank, and no Participant or beneficiary shall have any property interest in any specific assets of the Bank. To the extent a Participant or any other person acquires a right to receive payments from the Bank under this Plan, such right shall be no greater than the right of any unsecured general creditor of the Bank.

Article 5

Administration

5.1 Administrator. The Administrator of the Plan may delegate any of its administrative functions to another person, subject to revocation of such delegation at any time.

5.2 Discretion. The Administrator shall have the discretionary power and authority to determine the individuals who shall become Participants in the Plan. The Administrator shall also have the discretionary power and authority, which it shall exercise in good faith, to determine whether a Participant is entitled to a benefit under the Plan, the identity of a Participant’s beneficiary, and the amount and form of the benefit payable to any Participant or beneficiary. The Administrator shall have the discretion and authority to interpret the Plan and to make such rules and regulations as it deems necessary for the administration of the Plan and to carry out its purposes. The determinations of the Administrator shall be conclusive and binding on all persons.

5.3 Determination of Benefit. The Administrator’s good faith determination of the benefits to which a Participant, surviving spouse, or beneficiary is entitled under this Plan shall be conclusive and binding on all persons; provided, however, that this provision shall not preclude the Administrator’s correcting any error the Administrator determines to have been

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made in the computation of any benefit. The Administrator shall be entitled to recover from any Participant or beneficiary, or from his estate, the amount of any overpayment of benefits and may reduce the amount of future benefits payable to any Participant or beneficiary by the amount of any overpayment made with respect to the Participant.

5.4 Benefit Claim Procedure. Within a reasonable period of time following a Participant’s termination of employment, the Administrator will inform the Participant or the beneficiary of a deceased Participant of the amount of benefits, if any, payable from the Plan. Not later than 30 days after receipt of such notification, the Participant or beneficiary may file with the Administrator a written claim objecting to the amount of benefits payable under the Plan. The Administrator, not later than 90 days after receipt of such claim, will render a written decision to the claimant on the claim. If the claim is denied, in whole or in part, such decision will include the reason or reasons for the denial, a reference to the Plan provision that is the basis for the denial, a description of additional material or information, if any, necessary for the claimant to perfect the claim, an explanation as to why such information or material is necessary and an explanation of the Plan’s claim procedure. The claimant may file with the Administrator, not later than 60 days after receiving the Administrator’s written decision, a written notice of request for review of the decision, and the claimant or the claimant’s representative may review Plan documents which relate to the claim and may submit written comments to the Administrator. Not later than 60 days after receipt of such review request, the Administrator will render a written decision on the claim, which decision will include the specific reasons for the decision, including a reference to the Plan’s specific provisions where appropriate. The foregoing 90- and 60-day periods during which the Administrator must respond to the claimant may be extended by up to an additional 90 or 60 days, respectively, if special circumstances beyond the Administrator’s control so require.

5.5 Indemnification. The Bank shall indemnify the Administrator and each other person to whom administrative functions are delegated against any and all liabilities that may arise out of their administration of the Plan, except those that are imposed on account of such person’s willful misconduct.

5.6 Limitation of Authority. No person performing any administrative functions with respect to the Plan shall exercise, or participate in the exercise of, any discretion with respect to his own benefit under the Plan. This provision shall not preclude such person from exercising discretionary authority with respect to the generally applicable provisions of the Plan, even though such person’s benefit may be affected by such exercise.

Article 6

Miscellaneous

6.1 Actuarial Equivalency. Whenever an actuarial equivalent must be determined under this Plan, it shall be determined using reasonable actuarial factors elected by the Administrator.

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6.2 Termination of Employment. A Participant shall be deemed to have terminated employment for purposes of this Plan when he or she has ceased to provide service to the Bank as an employee.

6.3 Effective Date. This Plan is effective as of June 17, 2003.

6.4 No Employment Rights. Nothing contained in this Plan shall be construed as conferring upon any employee the right to continue in the employ of the Bank.

6.5 No Compensation Guarantees. Nothing contained in this Plan shall be construed as conferring upon any employee the right to receive any specific level of compensation; nor shall the Bank be prevented in any way from modifying the manner or form in which the employee is to be compensated.

6.6 Effect on Benefit Plans. Neither benefits accrued by a Participant under this Plan nor amounts paid pursuant to the Plan following the Participant’s termination of employment shall be deemed to be salary or other compensation to the Participant for the purpose of computing benefits to which he or she may be entitled under any pension plan or other employee benefit plan or arrangement sponsored by the Bank, except to the extent such other plan expressly provides otherwise.

6.7 Rights and Benefits Not Assignable. The rights and benefits of a Participant and any other person or persons to whom payments may be made pursuant to this Plan are personal and, except for payments made to the representative of a person’s estate which may be assigned to the persons entitled to such estate, shall not be subject to any voluntary or involuntary anticipation, alienation, sale, assignment, pledge, transfer, encumbrance, attachment, garnishment by creditors of the Participant or such person or other disposition.

6.8 Amendment and Termination.

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6.9 Governing Law. Except to the extent preempted by federal law, this Plan shall be construed in accordance with, and governed by, the laws of the State of Connecticut without regard to rules relating to choice of law.

6.10 Entire Agreement. This Plan constitutes the entire understanding between the Bank and each Participant as to the subject matter hereof. No rights are granted to a Participant by virtue of this Agreement other than those specifically set forth herein.

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APPENDIX A

Acceptance and Beneficiary Designation

I,                    , hereby designate                      as direct beneficiary and                      as contingent beneficiary of the [portion of] benefits payable under the terms of the Plan.

Signed at Willimantic, Connecticut, this      day of                      2003.

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Form of Benefit

In accordance with Section 3.6 of the Plan, I hereby elect to have my benefits under the Plan payable in the form of a:

IN WITNESS WHEREOF, the Bank and the executive execute the Plan as of the dates indicated below: