DEPOSIT AGREEMENT

Exhibit (4)(a)

DEPOSIT AGREEMENT

AMONG

S&T BANCORP, INC.

[              ],

as Depositary

and the Holders from time to time of

the Depository Receipts described herein

Dated as of                      ,             

TABLE OF CONTENTS

- i -

TABLE OF CONTENTS (cont’d)

- ii -

DEPOSIT AGREEMENT

DEPOSIT AGREEMENT, dated as of                      ,              among S&T BANCORP, INC., a Pennsylvania corporation, [              ], a [              ] corporation, as Depositary, and the holders from time to time of the Receipts described herein.

WITNESSETH

WHEREAS, it is desired to provide, as hereinafter set forth in this Deposit Agreement, for the deposit of shares of Series      [__%] Preferred Stock, no par value per share, of S&T Bancorp, Inc. with the Depositary (as hereinafter defined) for the purposes set forth in this Deposit Agreement and for the issuance hereunder of Receipts (as hereinafter defined) by the Depositary evidencing Depositary Shares in respect of the Stock (as hereinafter defined) so deposited;

NOW, THEREFORE, in consideration of the premises contained herein and such other good and valuable consideration, receipt of which is hereby acknowledged, the parties hereto agree as follows:

ARTICLE I

DEFINITIONS

SECTION 1.1. Definitions.

The following definitions shall for all purposes, unless otherwise indicated, apply to the respective terms used in this Deposit Agreement and the Receipts:

“Certificate of Designation” shall mean the certificate of designation to the Articles of Incorporation, as amended, of the Company filed with the Department of State of the Commonwealth of Pennsylvania establishing the Stock as a series of preferred stock of the Company.

“Company” shall mean S&T Bancorp, Inc., a Pennsylvania corporation, and its successors.

“Deposit Agreement” shall mean this Deposit Agreement, as amended or supplemented from time to time in accordance with the terms hereof.

“Depositary” shall mean [              ], a [              ] corporation, and any successor Depositary hereunder.

“Depositary Shares” shall mean the Depositary Shares, each representing a one-              (1/__th) interest in a share of Stock and which shall be evidenced by Receipts.

“Depositary’s Agent” shall mean an agent appointed by the Depositary pursuant to Section 7.5.

“Depositary’s Office” shall mean the principal office of the Depositary at which at any particular time its depositary business shall be administered.

“Receipt” shall mean one of the depositary receipts, whether in definitive or temporary form, issued hereunder by the Depositary, each representing any number of whole Depositary Shares. [If Receipts are to be issued in Book-Entry Form: If the context so requires, the term “Receipt” shall be deemed to include the DTC Receipt (as defined in Section 2.1 hereof).] “record holder” with respect to a Receipt shall mean the individual, entity or person in whose name a Receipt is registered on the books of the Depositary or any register of any Registrar maintained for such purpose at a given time.

“Registrar” shall mean any bank or trust company which shall be appointed by the Depositary to register ownership and transfers of Receipts as herein provided and which may include the Depositary.

“Securities Act” shall mean the Securities Act of 1933, as amended.

“Stock” shall mean shares of the Company’s Series      [              %] Preferred Stock, no par value per share.

ARTICLE II

FORM OF RECEIPTS; DEPOSIT OF STOCK; EXECUTION AND

DELIVERY, TRANSFER, SURRENDER AND REDEMPTION OF RECEIPTS

[Use bracketed portions only if Receipts are to be issued in Book-Entry Form]

Section 2.1. [Book-Entry Form;] Form and Transfer of Receipts .

(a) [[All] [A portion] of the Receipts shall initially be represented by one or more global receipts (collectively, the “DTC Receipt”) deposited with The Depository Trust Company (“DTC”) and registered in the name of [Cede & Co.], a nominee of DTC. The Depositary, or such other entity as is agreed to by DTC, may hold the DTC Receipt as custodian for DTC. So long as the Receipts are eligible for book-entry settlement with DTC, except as provided for in Section 2.9 hereof, no person acquiring Depositary Shares traded on any securities exchange with book-entry settlement through DTC shall receive or be entitled to receive physical delivery of the Receipts evidencing such Depositary Shares. Ownership of beneficial interests in the DTC Receipt shall be shown on, and the transfer of such ownership shall be effected through, records maintained by (i) DTC or its nominee for such DTC Receipt, or (ii) institutions that have accounts with DTC.]

- 2 -

(b) [If DTC subsequently ceases to make its book-entry settlement system available for the Receipts, the Company may instruct the Depositary regarding making other arrangements for book-entry settlement. In the event that the Receipts are not eligible for, or it is no longer necessary to have the Receipts available in, book-entry form, the Depositary shall provide written instructions to DTC to deliver to the Depositary for cancellation the DTC Receipt, and the Company shall instruct the Depositary to deliver to the beneficial owners of the Depositary Shares previously evidenced by the DTC Receipt definitive receipts in physical form evidencing such Depositary Shares. Such definitive Receipts shall be in the form annexed hereto as Exhibit A with appropriate insertions, modifications and omissions, as hereafter provided.]

(c) The beneficial owners of Depositary Shares shall [, except as stated above with respect to Depositary Shares in book-entry form represented by the DTC Receipt,] be entitled to receive Receipts in physical, certificated form as herein provided.

(d) [The Receipts may be typewritten in the case of the DTC Receipts and otherwise shall, upon notice by the Company to the Depositary, be definitive Receipts.] Definitive Receipts shall be engraved or printed or lithographed on steel-engraved borders and shall be substantially in the form annexed hereto as Exhibit A, with appropriate insertions, modifications and omissions, as hereinafter provided. [If Receipts are to be issued in Book-Entry Form: The DTC Receipt shall bear such legend or legends as may be required by DTC in order for it to accept the Depositary Shares for its book-entry settlement system.] Pending the preparation of definitive Receipts, the Depositary, upon the written order of the Company [If shares of Stock may be deposited by holders thereof: or any holder of Stock, as the case may be,] delivered in compliance with Section 2.2, shall execute and deliver temporary Receipts which shall be printed, lithographed, typewritten, mimeographed or otherwise substantially of the tenor of the definitive Receipts in lieu of which they are issued and with such appropriate insertions, omissions, substitutions and other variations as the persons executing such Receipts may determine, as evidenced by their execution of such Receipts. After the preparation of definitive Receipts, the temporary Receipts shall be exchangeable for definitive Receipts upon surrender of the temporary Receipts at the Depositary’s Office, without charge to the holder. Upon surrender for cancellation of any one or more temporary Receipts, the Depositary shall execute and deliver in exchange therefor definitive Receipts representing the same number of Depositary Shares as represented by the surrendered temporary Receipt or Receipts registered in the name (and only the name) of the holder of the temporary Receipt. Such exchange shall be made at the Company’s expense and without any charge therefor to the holder. Until so exchanged, the temporary Receipts shall in all respects be entitled to the same benefits under this Deposit Agreement and with respect to the Stock, as definitive Receipts.

(e) Receipts shall be executed by the Depositary by the manual signature of a duly authorized officer of the Depositary; provided, that such signature may be a facsimile if a Registrar for the Receipts (other than the Depositary) shall have been appointed and such Receipts are countersigned by manual signature of a duly authorized officer of the Registrar. No Receipt shall be entitled to any benefits under this Deposit Agreement or be valid or obligatory for any purpose unless it shall have been executed manually by a duly

- 3 -

authorized officer of the Depositary or, if a Registrar for the Receipts (other than the Depositary) shall have been appointed, by facsimile signature of a duly authorized officer of the Depositary and countersigned manually by a duly authorized officer of such Registrar. The Depositary shall record on its books each Receipt so signed and delivered as hereinafter provided. Receipts bearing the manual or facsimile signatures of individuals who were at any time proper officers of the Depositary or the Registrar, as the case may be, shall constitute adequate signatures hereunder, notwithstanding that such individuals or any of them have ceased to hold such offices prior to the delivery of such Receipts or did not hold such offices on the date of delivery of such Receipts.

Receipts shall be in denominations of any number of whole Depositary Shares.

(f) Receipts may be endorsed with or have incorporated in the text thereof such legends or recitals or changes not inconsistent with the provisions of this Deposit Agreement as may be required by the Depositary and approved by the Company or required to comply with any applicable law or regulation or with the rules and regulations of any securities exchange upon which the Stock, the Depositary Shares or the Receipts may be listed or to conform with any usage with respect thereto, or to indicate any special limitations or restrictions to which any particular Receipts are subject.

(g) [Subject to any limitations set forth in a Receipt or in this Deposit Agreement,] Title to Depositary Shares evidenced by a Receipt which is properly endorsed, or accompanied by a properly executed instrument of transfer, shall be transferable by delivery of such Receipt with the same effect as if such Receipt were a negotiable instrument; provided, however, that until transfer of a Receipt shall be registered on the books of the Registrar, on behalf of the Depositary, as provided in Section 2.4, the Depositary may, notwithstanding any notice to the contrary, treat the record holder as the absolute owner thereof for the purpose of determining the person entitled to distributions of dividends or other distributions with respect to the Stock[, the exchange of Depositary Shares for Stock, the right to exchange Receipts pursuant to Section 2.9] or to any notice provided for in this Deposit Agreement and for all other purposes.

The Depositary shall not lend any Stock deposited hereunder.

Section 2.2. Deposit of Stock; Execution and Delivery of Receipts in Respect Thereof .

(a) Subject to the terms and conditions of this Deposit Agreement, the Company [If shares of Stock may be deposited by holders thereof: or any holder of Stock] may from time to time deposit shares of Stock with the Depositary under this Deposit Agreement by delivery to the Depositary of a certificate or certificates representing the Stock to be deposited. Such certificate or certificates representing the Stock shall be properly endorsed or accompanied, if required by the Depositary, by a duly executed instrument of transfer or endorsement, in form satisfactory to the Depositary, together with all such certifications as may be required by the Depositary in accordance with the

- 4 -

provisions of this Deposit Agreement, and together with a written order of the Company [If shares of Stock may be deposited by holders thereof: or such holder, as the case may be,] directing the Depositary to execute and deliver to, or upon the written order of, the person or persons named in such order, a Receipt or Receipts evidencing in the aggregate the number of Depositary Shares representing such deposited Stock.

(b) All Stock deposited by the Company [If shares of Stock may be deposited by holders thereof: or any holder of Stock, as the case may be,] with the Depositary shall be held by the Depositary at the Depositary’s Office or at such other place or places as the Depositary shall determine.

(c) Upon receipt by the Depositary of a certificate or certificates representing Stock deposited, with the Depositary by the Company [If shares of Stock may be deposited by holders thereof: or any holder of Stock, as the case may be,] in accordance with the provisions of this Section, together with the other documents required as above specified, and upon recordation of the Stock so deposited on the books of the Company in the name of the Depositary, the Depositary shall execute and deliver, to the person or persons named in the written order delivered to the Depositary, a Receipt or Receipts, evidencing in the aggregate the number of Depositary Shares relating to the Stock so deposited. Such Receipt or Receipts shall be registered by the Depositary or the Registrar in such name or names as may be requested by the person or persons named in the written order. The Depositary shall execute and deliver such Receipts at the Depositary’s Office or such other offices, if any, as such person may designate. Delivery at other offices shall be at the risk and expense of the person requesting such delivery. [If Receipts are to be issued in Book-Entry Form: The DTC Receipt shall provide that it shall evidence the aggregate amount of Depositary Shares from time to time indicated in the records of the Depositary and that the aggregate amount of Depositary Shares evidenced thereby may from time to time be increased or decreased by making adjustments on such records of the Depositary.]

(d) Other than in the case of splits, combinations or other reclassifications affecting the Stock, or in the case of dividends or other distributions of Stock, if any, there shall be deposited with the Depositary hereunder not more than              shares of Stock.

Section 2.3. Redemption of Stock.

(a) Whenever the Company shall elect to redeem shares of Stock in accordance with the provisions of the Amendment, it shall (unless otherwise agreed in writing with the Depositary) mail notice to the Depositary of such redemption, by first class mail, postage prepaid, not less than 40 nor more than 70 days prior to the date fixed for the redemption of Stock in accordance with the provisions of the Amendment. On the date of such redemption, provided that the Company shall then have paid in full to the Depositary the redemption price required pursuant to the Amendment relating to the Stock to be redeemed, the Depositary shall redeem the Depositary Shares relating to such Stock. The Depositary shall mail notice of such redemption, and the simultaneous

- 5 -

redemption of the number of Depositary Shares relating to the Stock to be redeemed, by first-class mail, postage prepaid, not less than 30 and not more than 60 days prior to the date fixed for redemption of such Stock and Depositary Shares (the “Redemption Date”), to the record holders of the Receipts evidencing the Depositary Shares to be so redeemed on the record date fixed pursuant to Section 4.4 hereof, at the addresses of such holders as they appear on the records of the Depositary; provided, however, that neither failure to mail any such notice to one or more such holders nor any defect in any notice or in the mailing thereof to one or more such holders shall affect the validity of the proceedings for redemption of any Depositary Shares as to other holders. Each such notice of redemption shall state: (i) the Redemption Date; (ii) the number of Depositary Shares to be redeemed and, if less than all the Depositary Shares held by any such holder are to be redeemed, the number of such Depositary Shares held by such holder to be so redeemed and the method by which the Depositary Shares will be chosen for redemption; (iii) the redemption price (including cumulative dividends to the Redemption Date); (iv) the place or places where Receipts evidencing Depositary Shares are to be surrendered for payment of the redemption price; (v) that dividends in respect of the Stock to be redeemed, which are represented by the Depositary Shares to be redeemed, will cease to accrue at the close of business on such Redemption Date and (vi) if a date other than the Redemption Date, the date from and after which the Stock and Depositary Shares shall no longer be deemed to be outstanding. In case less than all the outstanding Depositary Shares are to be redeemed, the Depositary Shares to be so redeemed shall be selected by lot or pro rata as may be determined by the Company.

(b) Notice having been mailed by the Depositary as aforesaid, from and after (i) the Redemption Date (unless the Company shall have failed to redeem the shares of Stock to be redeemed by it as set forth in the Company’s notice provided for in the preceding paragraph), or (ii) such earlier date (if applicable) upon which the Company deposits the Redemption Price with the paying agent for the holders of the Stock (regardless of whether such shares are actually surrendered for cancellation), all dividends in respect of the shares of Stock so called for redemption shall cease to accrue, the Depositary Shares being redeemed from such proceeds shall be deemed no longer to be outstanding, all rights of the holders of Receipts evidencing such Depositary Shares (except the right to receive the redemption price) shall, to the extent of such Depositary Shares, cease and terminate and, upon surrender in accordance with such notice of the Receipts evidencing any such Depositary Shares called for redemption (properly endorsed or assigned for transfer, if the Depositary shall so require), such Depositary Shares shall be redeemed by the Depositary at a redemption price per Depositary Share equal to 1/__th of the redemption price per share paid in respect of the shares of Stock plus all money and other property, if any, underlying such Depositary Shares, including all amounts paid by the Company in respect of dividends which on the Redemption Date have accrued on the shares of Stock to be so redeemed and have not theretofore been paid.

(c) If less than all the Depositary Shares evidenced by a Receipt are called for redemption, the Depositary will deliver to the holder of such Receipt upon its surrender to the Depositary, together with the payment of the redemption price, a new Receipt

- 6 -

evidencing such number of Depositary Shares as were evidenced by such prior Receipt and not called for redemption; provided, however, that such replacement Receipt shall be issued only in denominations of whole Depositary Shares and cash will be payable in respect of fractional interests.

Section 2.4. Registration of Transfer of Receipts.

Subject to the terms and conditions of this Deposit Agreement, the Registrar, on behalf of the Depositary, shall register on its books transfers of Receipts from time to time upon notice to the Registrar by the Depositary of the surrender of a Receipt for transfer by the holder in person or by duly authorized attorney, which Receipt in each case must be properly endorsed or accompanied by a properly executed instrument of transfer. Upon surrender of a properly endorsed Receipt or Receipt accompanied by an instrument of transfer, the Depositary shall execute a new Receipt or Receipts evidencing the same aggregate number of Depositary Shares as those evidenced by the Receipt or Receipts surrendered and deliver such new Receipt or Receipts to or upon the order of the transferee named in the endorsement or instrument of transfer.

Section 2.5. Split-Ups and Combinations of Receipts; Surrender of Receipts and Withdrawal of Stock.

(a) Upon surrender of a Receipt or Receipts at the Depositary’s Office or at such other offices as it may designate for the purpose of effecting a split-up or combination of such Receipt or Receipts, the Depositary shall execute and deliver a new Receipt or Receipts to the holder thereof or to such holder’s order in the denominations requested, evidencing the aggregate number of Depositary Shares evidenced by the Receipt or Receipts surrendered. The Depositary shall give prompt notice of such action and the certificate numbers to the Registrar for the purpose of recording such split-up or consolidation.

(b) Unless the related Depositary Shares have previously been called for redemption, any holder of a Receipt or Receipts representing any number of whole shares of Stock (or such holder’s duly authorized attorney) may withdraw the number of whole shares of Stock underlying such Depositary Shares and all money and other property, if any, represented thereby by surrendering such Receipt or Receipts at the Depositary’s Office or at such other offices as the Depositary may designate for such withdrawals. [If Receipts are to be issued in Book-Entry Form: If such holder’s Depositary Shares are being held by DTC or its nominee pursuant to Section 2.1, such holder shall request, in accordance with Section 2.9, withdrawal from the book-entry system of the number of Depositary Shares specified in the preceding sentence.] Thereafter, without unreasonable delay, the Depositary shall deliver to such holder, or to the person or persons designated by such holder as hereinafter provided, the number of whole shares of Stock and all money and other property, if any, represented by the Receipt or Receipts so surrendered for withdrawal, but holders of such whole shares of Stock will not thereafter be entitled to deposit such Stock hereunder or to receive Depositary Shares therefor. If the Receipt or Receipts delivered by the holder to the Depositary in connection with such withdrawal

- 7 -

shall evidence in the aggregate a number of Depositary Shares in excess of the number of Depositary Shares representing the number of whole shares of Stock to be so withdrawn, the Depositary shall at the same time, in addition to such number of whole shares of Stock and such money and other property, if any, to be so withdrawn, deliver to such holder, or (subject to Sections 2.4 and 3.2) upon his order, a new Receipt evidencing such excess number of Depositary Shares. Delivery of the Stock and the money and other property being withdrawn may be made by the delivery of such certificates, documents of title and other instruments as the Depositary may deem appropriate.

(c) Stock delivered pursuant to the preceding paragraph may be endorsed with or have incorporated in the text thereof such legend or recitals or changes not inconsistent with the provisions of this Deposit Agreement as may be required by the Depositary or required to comply with any applicable law or any regulation thereunder or with the rules and regulations of any securities exchange upon which the Stock may be listed or to conform with any usage with respect thereto, or to indicate any special limitations or restrictions to which any particular shares of Stock are subject.

(d) If the Stock and the money and other property being withdrawn are to