Exhibit 3.1.1

CERTIFICATE OF DESIGNATION

OF

SERIES A JUNIOR PARTICIPATING PREFERRED STOCK

OF

PJT PARTNERS INC.

We, Michael S. Chae, as Chief Financial Officer, and Daniel Lee, as Assistant Secretary, of PJT Partners Inc., a Delaware corporation (the “Corporation”), in accordance with the provisions of Section 151(g) of the General Corporation Law of the State of Delaware, DO HEREBY CERTIFY:

That the Board of Directors adopted the following resolution creating a series of Preferred Stock designated as Series A Junior Participating Preferred Stock:

RESOLVED, that pursuant to the authority vested in the Board of Directors in accordance with the provisions of the Certificate of Incorporation, a series of Preferred Stock of the Corporation be, and it hereby is, created, and that the designation and amount thereof and the powers, preferences and relative, participating, optional and other special rights of the shares of such series, and the qualifications, limitations or restrictions thereof are as follows:

SECTION 1. Designation and Amount. The shares of such series shall be designated as “Series A Junior Participating Preferred Stock,” par value $0.01 per share (the “Series A Junior Participating Preferred Stock”), and the number of shares constituting such series shall be 3,000,000, which number may from time to time be increased or decreased (but not below the number then outstanding) by the Board of Directors.

SECTION 2. Dividends and Distributions. (a) The dividend rate on the shares of Series A Junior Participating Preferred Stock shall be for each quarterly dividend (hereinafter referred to as a “Quarterly Dividend Period”), which Quarterly Dividend Periods shall commence on January 1, April 1, July 1 and October 1 each year (each such date being referred to herein as a “Quarterly Dividend Payment Date”) (or in the case of original issuance, from the date of original issuance) and shall end on and include the day next preceding the first date of the next Quarterly Dividend Period, at a rate per Quarterly Dividend Period (rounded to the nearest cent) subject to the provisions for adjustment hereinafter set forth, equal to the greater of (a) $1.000 and (b) 1,000 times the aggregate per share amount of all cash dividends, and 1,000 times the aggregate per share amount (payable in cash, based upon the fair market value at the time the non-cash dividend or other distribution is declared as determined in good faith by the Board of Directors) of all non-cash dividends or other distributions other than a dividend payable in shares of common stock or a subdivision of the outstanding shares of common stock (by reclassification or otherwise), declared (but not withdrawn) on the Class A Common Stock, par value $0.01 per share, of the Corporation (the “Common Stock”) during the immediately preceding quarterly dividend period, or, with respect to the first quarterly dividend period, since the first issuance of any share or fraction of a share of Series A Junior Participating Preferred Stock. In the event the Corporation shall at any time after October 1, 2015 (the “Rights Declaration Date”) (i) declare

any dividend on Common Stock payable in shares of Common Stock, (ii) subdivide the outstanding Common Stock, or (iii) combine the outstanding Common Stock into a smaller number of shares, then in each such case the amount to which holders of shares of Series A Junior Participating Preferred Stock were entitled immediately prior to such event under the preceding sentence shall be adjusted by multiplying such amount by a fraction the numerator of which is the number of shares of Common Stock outstanding immediately after such event and the denominator of which is the number of shares of Common Stock that were outstanding immediately prior to such event.

(b) Dividends shall begin to accrue and be cumulative on outstanding shares of Series A Junior Participating Preferred Stock from the Quarterly Dividend Payment Date next preceding the date of issue of such shares of Series A Junior Participating Preferred Stock, unless the date of issue of such shares is prior to the record date for the first Quarterly Dividend Payment Date, in which case dividends on such shares shall begin to accrue from the date of issue of such shares, or unless the date of issue is a Quarterly Dividend Payment Date or is a date after the record date for the determination of holders of shares of Series A Junior Participating Preferred Stock entitled to receive a quarterly dividend and before such Quarterly Dividend Payment Date, in either of which events such dividends shall begin to accrue and be cumulative from such Quarterly Dividend Payment Date. Accrued but unpaid dividends shall not bear interest. Dividends paid on the shares of Series A Junior Participating Preferred Stock in an amount less than the total amount of such dividends at the time accrued and payable on such shares shall be allocated pro rata on a share-by-share basis among all such shares at the time outstanding. The Board of Directors may fix a record date for the determination of holders of shares of Series A Junior Participating Preferred Stock entitled to receive payment of a dividend or distribution declared thereon, which record date shall be no more than 45 days prior to the date fixed for the payment thereof.

(c) So long as any shares of the Series A Junior Participating Preferred Stock are outstanding, no dividends or other distributions shall be declared, paid or distributed, or set aside for payment or distribution, on the Common Stock unless, in each case, the dividend required by this Section 2 to be declared on the Series A Junior Participating Preferred Stock shall have been declared.

(d) The holders of the shares of Series A Junior Participating Preferred Stock shall not be entitled to receive any dividends or other distributions except as provided herein.

SECTION 3. Voting Rights. The holders of shares of Series A Junior Participating Preferred Stock shall have the following voting rights:

(a) Subject to the provision for adjustment hereinafter set forth, each share of Series A Junior Participating Preferred Stock shall entitle the holder thereof to 1,000 votes on all matters submitted to a vote of the stockholders of the Corporation. In the event the Corporation shall at any time after the Rights Declaration Date (i) declare any dividend on Common Stock payable in shares of Common Stock, (ii) subdivide the outstanding Common Stock, or (iii) combine the outstanding Common Stock into a smaller number of shares, then in each such case the number of votes per share to which holders of shares of Series A Junior Participating Preferred Stock were entitled immediately prior to such event shall be adjusted by multiplying such number by a

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fraction the numerator of which is the number of shares of Common Stock outstanding immediately after such event and the denominator of which is the number of shares of Common Stock that were outstanding immediately prior to such event.

(b) Except as otherwise provided herein, in the Certificate of Incorporation or the Amended and Restated Bylaws of the Corporation (the “Bylaws”) or by applicable law, the holders of shares of Series A Junior Participating Preferred Stock and the holders of shares of Common Stock shall vote together as one class for the election of directors of the Corporation and on all other matters submitted to a vote of stockholders of the Corporation.

(c) Except as set forth herein, in the Certificate of Incorporation or the Bylaws or by applicable law, holders of Series A Junior Participating Preferred Stock shall have no special voting rights and their consent shall not be required (except to the extent they are entitled to vote with holders of Common Stock as set forth herein) for authorizing or taking any corporate action.

(d) If, at the time of any annual meeting of stockholders for the election of directors, the equivalent of six quarterly dividends (whether or not consecutive) payable on any share or shares of Series A Junior Participating Preferred Stock are in default, the number of directors constituting the Board of Directors shall be increased by two. In addition to voting together with the holders of Common Stock for the election of other directors of the Corporation, the holders of record of the Series A Junior Participating Preferred Stock, voting separately as a class to the exclusion of the holders of Common Stock, shall be entitled at said meeting of stockholders (and at each subsequent annual meeting of stockholders), unless all dividends in arrears have been paid or declared and set apart for payment prior thereto, to vote for the election of two directors of the Corporation, the holders of any Series A Junior Participating Preferred Stock being entitled to cast a number of votes per share of Series A Junior Participating Preferred Stock as is specified in paragraph (a) of this Section 3. Until the default in payments of all dividends which permitted the election of said directors shall cease to exist, any director who shall have been so elected pursuant to the preceding sentence may be removed at any time, either with or without cause, only by the affirmative vote of the holders of the shares of Series A Junior Participating Preferred Stock at the time entitled to cast a majority of the votes entitled to be cast for the election of any such director at a special meeting of such holders called for that purpose, and any vacancy thereby created may be filled by the vote of such holders. If and when such default shall cease to exist, the holders of the Series A Junior Participating Preferred Stock shall be divested of the foregoing special voting rights, subject to revesting in the event of each and every subsequent like default in payments of dividends. Upon the termination of the foregoing special voting rights, the terms of office of all persons who may have been elected directors pursuant to said special voting rights shall forthwith terminate, and the number of directors constituting the Board of Directors shall be reduced by two. The voting rights granted by this Section 3(d) shall be in addition to any other voting rights granted to the holders of the Series A Junior Participating Preferred Stock in this Section 3.

SECTION 4. Reacquired Shares. Any shares of Series A Junior Participating Preferred Stock purchased or otherwise acquired by the Corporation in any manner whatsoever shall be retired and canceled promptly after the acquisition thereof. All such shares shall upon their cancelation become authorized but unissued shares of Preferred Stock, without designation as to series until such shares are once more designated as part of a particular series by the Board of Directors pursuant to the provisions of the Certificate of Incorporation.

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SECTION 5. Liquidation, Dissolution or Winding Up. Upon the liquidation, dissolution or winding up of the Corporation, whether voluntary or involuntary, no distribution shall be made (1) to the holders of shares of stock ranking junior (either as to dividends or upon liquidation, dissolution or winding up) to the Series A Junior Participating Preferred Stock unless, prior thereto, the holders of shares of Series A Junior Participating Preferred Stock shall have received an amount equal to the accrued and unpaid dividends and distributions thereon, whether or not declared, to the date of such payment, plus an amount per share, subject to the provision for adjustment hereinafter set forth, equal to 1,000 times the aggregate amount to be distributed per share to holders of Common Stock or (2) to the holders of stock ranking on parity (either as to dividends or upon liquidation, dissolution or winding up) to the Series A Junior Participating Preferred Stock except distributions made ratably on the Series A Junior Participating Preferred Stock and all other such parity stock in proportion to the total amounts to which the holders of all such shares are entitled upon such liquidation, dissolution or winding up. In the event the Corporation shall at any time after the Rights Declaration Date (i) declare any dividend on Common Stock payable in shares of Common Stock, (ii) subdivide the outstanding Common Stock, or (iii) combine the outstanding Common Stock into a smaller number of shares, then in each such case the amount to which holders of shares of Series A Junior Participating Preferred Stock were entitled immediately prior to such event pursuant to clause (2) of the preceding sentence shall be adjusted by multiplying such amount by a fraction the numerator of which is the number of shares of Common Stock outstanding immediately after such event and the denominator of which is the number of shares of Common Stock that were outstanding immediately prior to such event.

SECTION 6. Consolidation, Merger, etc. In case the Corporation shall enter into any consolidation, merger, combination or other transaction in which the shares of Common Stock are exchanged for or changed into other stock or securities, cash and/or any other property, then in any such case the then outstanding shares of Series A Junior Participating Preferred Stock shall at the same time be similarly exchanged or changed into an amount per share (subject to the provision for adjustment hereinafter set forth) equal to 1,000 times the aggregate amount of stock, securities, cash and/or any other property (payable in kind), as the case may be, into which or for which each share of Common Stock is exchanged or changed. In the event the Corporation shall at any time after the Rights Declaration Date (i) declare any dividend on Common Stock payable in shares of Common Stock, (ii) subdivide the outstanding Common Stock, or (iii) combine the outstanding Common Stock into a smaller number of shares, then in each such case the amount set forth in the preceding sentence with respect to the exchange or change of shares of Series A Junior Participating Preferred Stock shall be adjusted by multiplying such amount by a fraction the numerator of which is the number of shares of Common Stock outstanding immediately after such event and the denominator of which is the number of shares of Common Stock that were outstanding immediately prior to such event.

SECTION 7. No Redemption; No Sinking Fund. (a) The shares of Series A Junior Participating Preferred Stock shall not be subject to redemption by the Corporation or at the option of any holder of Series A Junior Participating Preferred Stock; provided, however, that the Corporation may purchase or otherwise acquire outstanding shares of Series A Junior Participating Preferred Stock in the open market or by offer to any holder or holders of shares of Series A Junior Participating Preferred Stock.

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(b) The shares of Series A Junior Participating Preferred Stock shall not be subject to or entitled to the operation of a retirement or sinking fund.

SECTION 8. Fractional Shares. The Series A Junior Participating Preferred Stock shall be issuable upon exercise of the Rights issued pursuant to the Rights Agreement in whole shares or in any fraction of a share that is one one-thousandths (1/1,000ths) of a share or any integral multiple of such fraction which shall entitle the holder, in proportion to such holder’s fractional shares, to receive dividends, exercise voting rights, participate in distributions and to have the benefit of all other rights of holders of Series A Junior Participating Preferred Stock. In lieu of fractional shares, the Corporation, prior to the first issuance of a share or a fraction of a share of Series A Junior Participating Preferred Stock, may elect (1) to make a cash payment as provided in the Rights Agreement for fractions of a share other than one one-thousandths (1/1,000ths) of a share or any integral multiple thereof or (2) to issue depository receipts evidencing such authorized fraction of a share of Series A Junior Participating Preferred Stock pursuant to an appropriate agreement between the Corporation and a depository selected by the Corporation; provided that such agreement shall provide that the holders of such depository receipts shall have all the rights, privileges and preferences to which they are entitled as holders of the Series A Junior Participating Preferred Stock. All payments made with respect to fractional shares hereunder shall be rounded to the nearest whole cent.

SECTION 9. Certain Restrictions. (a) Whenever quarterly dividends or other dividends or distributions payable on the Series A Junior Participating Preferred Stock as provided in Section 2 are in arrears, thereafter and until all accrued and unpaid dividends and distributions, whether or not declared, on shares of Series A Junior Participating Preferred Stock outstanding shall have been paid in full, the Corporation shall not:

(i) declare or pay dividends on, make any other distributions on, or redeem or purchase or otherwise acquire for consideration any shares of stock ranking junior (either as to dividends or upon liquidation, dissolution or winding up) to the Series A Junior Participating Preferred Stock;

(ii) declare or pay dividends on or make any other distributions on any shares of stock ranking on a parity (either as to dividends or upon liquidation, dissolution or winding up) with the Series A Junior Participating Preferred Stock, except dividends paid ratably on the Series A Junior Participating Preferred Stock and all such parity stock on which dividends are payable or in arrears in proportion to the total amounts to which the holders of all such shares are then entitled;

(iii) redeem or purchase or otherwise acquire for consideration shares of any stock ranking on a parity (either as to dividends or upon liquidation, dissolution or winding up) with the Series A Junior Participating Preferred Stock; provided that the Corporation may at any time redeem, purchase or otherwise acquire shares of any such parity stock in exchange for shares of any stock of the Corporation ranking junior (either as to dividends or upon liquidation, dissolution or winding up) to the Series A Junior Participating Preferred Stock; or

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(iv) purchase or otherwise acquire for consideration any shares of Series A Junior Participating Preferred Stock, or any shares of stock ranking on a parity with the Series A Junior Participating Preferred Stock, except in accordance with a purchase offer made in writing or by publication (as determined by the Board of Directors) to all holders of such shares upon such terms as the Board of Directors, after consideration of the respective annual dividend rates and other relative rights and preferences of the respective series and classes, shall determine in good faith will result in fair and equitable treatment among the respective series or classes.

(b) The Corporation shall not permit any subsidiary of the Corporation to purchase or otherwise acquire for consideration any shares of stock of the Corporation unless the Corporation could, under paragraph (a) of this Section 9, purchase or otherwise acquire such shares at such time and in such manner.

SECTION 10. Ranking. The Series A Junior Participating Preferred Stock shall rank junior to all other series of Preferred Stock of the Corporation but senior to each of the Common Stock and Class B Common Stock, par value $0.01 per share, of the Corporation as to dividends and upon liquidation, unless the Board of Directors shall specifically determine otherwise in fixing the powers, preferences and relative, participating, optional and other special rights of the shares of such series and the qualifications, limitations or restrictions thereof.

SECTION 11. Amendment. None of the powers, preferences and relative, participating, optional and other special rights of the Series A Junior Participating Preferred Stock as provided herein or in the Certificate of Incorporation shall be amended in any manner which would alter or change the powers, preferences, rights or privileges of the holders of Series A Junior Participating Preferred Stock so as to affect them adversely without the affirmative vote of the holders of at least two-thirds of the outstanding shares of Series A Junior Participating Preferred Stock, voting together as a single class.

This Certificate of Designation shall be effective at 12:02 A.M. eastern time on October 1, 2015.

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IN WITNESS WHEREOF, the Corporation has caused this Certificate of Designation to be duly executed in its corporate name on this day of September 30, 2015.