Adicet Bio, Inc.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A INFORMATION

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

(Amendment No. )

Check the appropriate box:

☐ Preliminary Proxy Statement

☐Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

☒ Definitive Proxy Statement

☐ Definitive Additional Materials

☐ Soliciting Material under §240.14a-12

Adicet Bio, Inc.

(Name of Registrant as Specified in its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

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ADICET BIO, INC.

131 Dartmouth Street, 3rd Floor

NOTICE OF 2026 ANNUAL MEETING OF STOCKHOLDERS

To be held on June 17, 2026

Notice is hereby given that the 2026 Annual Meeting of Stockholders (Annual Meeting) of Adicet Bio, Inc., will be held online on June 17, 2026 at 5:00 p.m. Eastern Time. You may attend the meeting virtually via the Internet atwww.virtualshareholdermeeting.com/ACET2026, where you will be able to vote electronically and submit questions. You will need the 16-digit control number included with the Notice of Internet Availability of Proxy Materials being mailed to you separately in order to attend the Annual Meeting.

The purpose of the Annual Meeting is the following:

To elect three class II directors to our board of directors, to serve until the 2029 annual meeting of stockholders and until his or her successor has been duly elected and qualified, or until his or her earlier death, resignation or removal;

To approve, on a non-binding advisory basis, the compensation of our named executive officers;

To ratify the appointment of KPMG LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2026; and

To transact any other business properly brought before the Annual Meeting or any adjournment or postponement of the Annual Meeting.

Only Adicet Bio, Inc. stockholders of record at the close of business on April 21, 2026, will be entitled to vote at the Annual Meeting and any adjournment or postponement thereof.

We are pleased to take advantage of the Securities and Exchange Commission’s “Notice and Access” rules that allow companies to furnish their proxy materials over the Internet. We are mailing to our stockholders a Notice of Internet Availability of Proxy Materials (Notice) instead of a paper copy of our proxy materials and our 2025 Annual Report to Stockholders (2025 Annual Report). We plan to mail the Notice on or about April 29, 2026, which will contain instructions on how to access those documents and to cast your vote via the Internet as well as instructions on how to request a paper copy of our proxy materials and our 2025 Annual Report. This process allows us to provide our stockholders with the information they need on a timelier basis, while reducing the environmental impact and lowering the costs of printing and distributing our proxy materials.

To be admitted to the Annual Meeting and vote your shares, you must provide the 16-digit control number as provided described in the Notice, or proxy card, or voting instruction form atwww.proxyvote.com. Please see the “General Information” section of the proxy statement that accompanies this notice for more details regarding the logistics of the virtual Annual Meeting, including the ability of stockholders to submit questions during the Annual Meeting, and technical details and support related to accessing the virtual platform.

Your vote is important. Whether or not you are able to attend the meeting in person, it is important that your shares be represented. To ensure that your vote is recorded promptly, please vote as soon as possible, even if you plan to attend the meeting, by submitting your proxy via the Internet at the address listed on the proxy card or by signing, dating, and returning the proxy card. If your shares are held in "street name," that is, held for your account by a broker or other nominee, you will receive instructions from the holder of record that you must follow for your shares to be voted.

By order of the board of directors,

/s/ Chen Schor

Chen Schor

President, Chief Executive Officer

Boston, Massachusetts

April 29, 2026

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