Instil Bio, Inc.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934

Filed by the Registrantx

Filed by a Party other than the Registranto

Check the appropriate box:

Instil Bio, Inc.

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement if Other Than the Registrant)

Payment of Filing Fee (Check the appropriate box)

3963 Maple Avenue, Suite 350

Dallas, Texas 75219

NOTICE OF ANNUAL MEETING OF STOCKHOLDERS

To Be Held On June 11, 2026

Dear Stockholder:

You are cordially invited to attend the 2026 Annual Meeting of Stockholders (the “Annual Meeting”) of INSTIL BIO, INC., a Delaware corporation (the “Company”). The meeting will be held on Thursday, June 11, 2026 at 11:00 a.m., Central Time at our corporate headquarters located at 3963 Maple Avenue, Suite 350, Dallas, Texas 75219 for the following purposes:

1. To elect the Board of Directors’ two director nominees, George Matcham and Neil Gibson, as Class II directors to hold office until the 2029 Annual Meeting of Stockholders.

2. To ratify the selection by the Audit Committee of the Board of Directors of RSM US LLP as the independent registered public accounting firm of the Company for the year ending December 31, 2026.

3. To conduct any other business properly brought before the meeting.

These items of business are more fully described in the Proxy Statement accompanying this Notice.

The record date for the Annual Meeting is April 13, 2026 (the “Record Date”). Only stockholders of record at the close of business on that date may vote at the meeting or any adjournment thereof.

Important Notice Regarding the Availability of Proxy Materials for the Stockholders’ Meeting to BeHeld on June 11, 2026 at 11:00 a.m., Central Time.The proxy statement and annual report to stockholdersare available at http://www.proxyvote.com.

By order of the Board of Directors,

/s/ Sandeep Laumas, M.D.

Sandeep Laumas, M.D.

Chief Financial Officer and Chief Business Officer

Dallas, TX

April 24, 2026

You are cordially invited to attend the Annual Meeting. Whether or not you expect to attend the meeting, please vote over the telephone or the internet as instructed in these materials, or, if you receive a paper proxy card by mail, by completing and returning the proxy mailed to you as promptly as possible in order to ensure your vote is counted at the meeting. Even if you have voted by proxy, you may still vote if you attend the Annual Meeting. Please note, however, that if your shares are held of record by a broker, bank or other nominee and you wish to vote at the meeting, you must obtain a proxy issued in your name from that record holder.

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