Terrestrial Energy Inc. /DE/

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

Check the appropriate box:

TERRESTRIAL ENERGY 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 all boxes that apply):

Terrestrial Energy Inc.

2730 W. Tyvola Road, Suite 100

Charlotte, NC 28217

(646) 687-8212

April 29, 2026

To the Stockholders of Terrestrial Energy Inc.:

We are pleased to invite you to attend the 2026 Annual Meeting of Stockholders (together with any adjournments or postponements thereof, the “Annual Meeting”) of Terrestrial Energy Inc. (the “Company”). The Annual Meeting will be held solely by means of remote communication via live webcast on Thursday, June 11, 2026 at 10:00 a.m. Eastern time. You may attend the Annual Meeting via live webcast at www.virtualshareholdermeeting.com/IMSR2026. During the Annual Meeting, you may submit questions and, prior to and during the Annual Meeting until polls are closed, you may vote by logging into www.virtualshareholdermeeting.com/IMSR2026 using your stockholder information provided on the Notice of Internet Availability of Proxy Materials described below.

As permitted by the rules of the U.S. Securities and Exchange Commission, we are furnishing our proxy materials to stockholders primarily over the Internet. We sent a Notice of Internet Availability of Proxy Materials on or about April 29, 2026, to our stockholders of record at the close of business on April 20, 2026. The notice contains instructions on how to access our Proxy Statement and Fiscal 2025 Annual Report and vote online. If you would like to receive a printed copy of our proxy materials, please follow the instructions for requesting such materials included in the notice.

We sincerely hope that you can attend the Annual Meeting. Even if you plan to attend the Annual Meeting, we encourage you to review these proxy materials and submit your voting instructions in advance of the Annual Meeting by Internet, by telephone, or by mail. Instructions regarding submitting a proxy by Internet and telephone are included on the proxy card.

Terrestrial Energy Inc.

2730 W. Tyvola Road, Suite 100

Charlotte, NC 28217

(646) 687-8212

NOTICE OF ANNUAL MEETING OF STOCKHOLDERS

TO BE HELD ON JUNE 11, 2026 AT 10:00 A.M.

The 2026 Annual Meeting of Stockholders of Terrestrial Energy Inc. (the “Company”) will be held solely by means of remote communication via live webcast at www.virtualshareholdermeeting.com/IMSR2026 on Thursday June 11, 2026 at 10:00 a.m. Eastern time (together with and any adjournments or postponements thereof, the “Annual Meeting”) for the following purposes:

The Board of Directors is not aware of any other business to come before the Annual Meeting.

We have fixed April 20, 2026 as the record date for the determination of stockholders entitled to notice of and to vote at the Annual Meeting. Only holders of record of the Company’s common stock and the Company’s special voting preferred stock at the close of business on that date will be entitled to notice of and to vote at the Annual Meeting and they or their proxy holders may be deemed to be present in person and vote at the Annual Meeting by means of remote communication via live webcast. You are cordially invited to attend the Annual Meeting. Whether or not you plan to attend the Annual Meeting, your vote is important, and we encourage you to review these proxy materials and submit your voting instructions in advance of the Annual Meeting by Internet, telephone, or mail, as described in the enclosed proxy statement or on the enclosed proxy card. You may also vote your shares electronically at the Annual Meeting. You will be able to attend the Annual Meeting online and submit your questions during the Annual Meeting by visiting www.virtualshareholdermeeting.com/IMSR2026.

The Board of Directors recommends that stockholders vote “FOR” each of the three director nominees and “FOR” the ratification of the appointment of UHY LLP as the Company’s independent registered public accounting firm for the fiscal year ending December 31, 2026.

You may revoke your proxy at any time prior to or at the Annual Meeting by written notice to the Company, by executing a proxy bearing a later date, or by attending the Annual Meeting and voting electronically at the Annual Meeting.

Important Notice Regarding the Availability of Proxy Materials for the Annual Meeting to be held on June 11, 2026: the Proxy Statement and the Company’s Annual Report on Form 10-K are available at****www.proxyvote.com.

TERRESTRIAL ENERGY INC.

April 29, 2026

PROXY STATEMENT FOR THE 2026 ANNUAL MEETING OF STOCKHOLDERS

TO BE HELD ON JUNE 11, 2026

The Board of Directors (the “Board of Directors” or “Board”) of Terrestrial Energy Inc. (the “Company”) is furnishing you this proxy statement to solicit, on its behalf, proxies to be voted at the Company’s 2026 Annual Meeting of Stockholders (together with and any adjournments or postponements thereof, the “Annual Meeting”) to be held on Thursday, June 11, 2026 at 10:00 a.m. Eastern time, solely by means of remote communication via live webcast at www.virtualshareholdermeeting.com/IMSR2026. These proxy materials are first being mailed or made available to stockholders on or about April 29, 2026.

The entire cost of soliciting these proxies will be borne by the Company. In addition to the delivery of the proxy materials by mail, the Company may request banks, brokers, and other record holders, or a proxy solicitor acting on its behalf, to send proxies and proxy materials to the beneficial owners of the Company’s Common Stock, par value $0.0001 per share (“Common Stock”), and to secure the voting instructions of such beneficial owners. The Company will reimburse any such banks, brokers, other record holders, or proxy solicitors acting on its behalf for their reasonable expenses in so doing. The Company has not engaged a proxy solicitor to solicit proxies from stockholders; however, the Company retains the right to do so if it deems such solicitation necessary. Furthermore, the Company may also use one or more of its current employees, who will not be specially compensated, to solicit proxies from stockholders in person, by telephone, by e-mail, or by special letter.

The Annual Meeting will be held for the purpose of considering and voting upon the following:

The Board is not aware of any other business to come before the Annual Meeting.

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