Exhibit 3.1

AMENDED AND RESTATED CERTIFICATE OF INCORPORATION

OF

BYLINE BANCORP, INC.

Byline Bancorp, Inc., a Delaware corporation (the “Corporation”), hereby certifies as follows:

FIRST. The name of the Corporation is Byline Bancorp, Inc.

SECOND. The address of the Corporation’s registered office in the State of Delaware is 2711 Centerville Road, Suite 400, in the City of Wilmington, County of New Castle, Zip Code 19808. The name of its registered agent at such address is Corporation Service Company.

THIRD. The purpose of the Corporation is to engage in any lawful act or activity for which corporations may be organized under the DGCL.

FOURTH. The total number of shares of all classes of stock which the corporation shall have authority to issue is 175 million, of which 150 million shares of the par value of $0.01 per share shall be designated as Common Stock and 25 million shares of the par value of $0.01 per share shall be designated as Preferred Stock.

Shares of Preferred Stock may be issued in one or more series from time to time by the Board of Directors, and the Board of Directors is expressly authorized to fix by resolution or resolutions the designations and the powers, preferences and rights, and the qualifications, limitations and restrictions thereof, of the shares of each series of Preferred Stock, including, without limitation, the following:

(a) the distinctive serial designation of such series which shall distinguish it from other series;

(b) the number of shares included in such series;

(c) the dividend rate (or method of determining such rate) payable to the holders of the shares of such series, any conditions upon which such dividends shall be paid and the date or dates upon which such dividends shall be payable;

(d) whether dividends on the shares of such series shall be cumulative and, in the case of shares of any series having cumulative dividend rights, the date or dates or method of determining the date or dates from which dividends on the shares of such series shall be cumulative;

(e) the amount or amounts which shall be payable out of the assets of the corporation to the holders of the shares of such series upon voluntary or involuntary liquidation, dissolution or winding up of the corporation, and the relative rights of priority, if any, of payment of the shares of such series;

(f) the price or prices at which, the period or periods within which and the terms and conditions upon which the shares of such series may be redeemed, in whole or in part, at the option of the corporation or at the option of the holder or holders thereof or upon the happening of a specified event or events;

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(g) the obligation, if any, of the corporation to purchase or redeem shares of such series pursuant to a sinking fund or otherwise and the price or prices at which, the period or periods within which and the terms and conditions upon which the shares of such series shall be redeemed or purchased, in whole or in part, pursuant to such obligation;

(h) whether or not the shares of such series shall be convertible or exchangeable, at any time or times at the option of the holder or holders thereof or at the option of the corporation or upon the happening of a specified event or events, into shares of any other class or classes or any other series of the same or any other class or classes of stock of the corporation, and the price or prices or rate or rates of exchange or conversion and any adjustments applicable thereto;

(i) whether or not the holders of the shares of such series shall have voting rights, in addition to the voting rights provided by law, and if so, the terms of such voting rights; and

(j) any other powers, preferences and rights and qualifications, limitations and restrictions not inconsistent with the DGCL.

For all purposes, this Certificate of Incorporation shall include each certificate of designations setting forth the terms of a series of Preferred Stock.

Unless otherwise provided in the resolution or resolutions of the Board of Directors or a duly authorized committee thereof establishing the terms of a series of Preferred Stock, no holder of any share of Preferred Stock shall be entitled as of right to vote on any amendment or alteration of the Certificate of Incorporation to authorize or create, or increase the authorized amount of, any other class or series of Preferred Stock or any alteration, amendment or repeal of any provision of any other series of Preferred Stock that does not adversely affect in any material respect the rights of the series of Preferred Stock held by such holder.

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Except as otherwise required by the DGCL or provided in the resolution or resolutions of the Board of Directors or a duly authorized committee thereof establishing the terms of a series of Preferred Stock, no holder of Common Stock, as such, shall be entitled to vote on any amendment or alteration of the Certificate of Incorporation that alters, amends or changes the powers, preferences, rights or other terms of one or more outstanding series of Preferred Stock if the holders of such affected series are entitled, either separately or together with the holders of one or more other series of Preferred Stock, to vote thereon pursuant to the Certificate of Incorporation or pursuant to the DGCL.

Subject to the rights of the holders of any series of Preferred Stock, the number of authorized shares of any class or series of Preferred Stock may be increased or decreased (but not below the number of shares thereof then outstanding) by the affirmative vote of the holders of a majority of the outstanding shares of such class or series, voting together as a single class, irrespective of the provisions of Section 242(b)(2) of the DGCL or any corresponding provision hereafter enacted.

Unless otherwise provided in the resolution or resolutions of the Board of Directors or a duly authorized committee thereof establishing the terms of a series of Preferred Stock, no holder of any share of Preferred Stock shall, in such capacity, be entitled to bring a derivative action, suit or proceeding on behalf of the Corporation.

FIFTH. The Board of Directors of the Corporation is expressly authorized to adopt, amend or repeal by-laws of the Corporation.

SIXTH. Elections of directors need not be by written ballot except and to the extent provided in the by-laws of the corporation.

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SEVENTH. The number of directors of the corporation shall be fixed from time to time pursuant to the by-laws of the corporation.

EIGHTH. No action required or permitted to be taken by the holders of any class or series of stock of the corporation, including but not limited to the election of directors, may be taken by one or more written consents.

NINTH. To the fullest extent authorized by the DGCL, a director of the corporation shall not be liable to the corporation or its stockholders for monetary damages for breach of such director’s fiduciary duty as a director, except to the extent that such exemption from liability or limitation thereof is not permitted under the DGCL as currently in effect or as the same may hereafter be amended.

To the fullest extent permitted by the DGCL, the corporation is authorized to provide indemnification of (and advancement of expenses to) the corporation’s directors, officers, employees and agents (and any other persons to which the DGCL permits the corporation to provide indemnification) through the Corporation’s by-laws, agreements with such persons, vote of stockholders or disinterested directors or otherwise, in excess of the indemnification and advancement otherwise permitted by Section 145 of the DGCL, subject only to limits created by applicable Delaware law (statutory or non-statutory), with respect to actions for breach of duty to the corporation, its stockholders and others, and by any applicable federal or state bank regulatory laws or regulations. Such right to indemnification and advancement of expenses shall continue as to a person who has ceased to be a director, officer, employee or agent and shall inure to the benefit of the heirs, executors and administrators of such a person.

No amendment, modification or repeal of this Article NINTH shall adversely affect any right or protection of a director, officer, employee or agent or other person existing at the time of, or increase the liability of any person with respect to any acts or omissions of such person occurring prior to, such amendment, modification or repeal.

TENTH. The corporation expressly elects not to be governed by Section 203 of the DGCL.

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IN WITNESS WHEREOF, Byline Bancorp, Inc. has caused this certificate to be signed by Alberto J. Paracchini, its President and Chief Executive Officer, on the 16th day of June, 2017.

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