SeaStar Medical Holding Corp

This proxy statement (the “Proxy Statement”) is furnished in connection with the solicitation by the Board of Directors of SeaStar Medical Holding Corporation of proxies to be voted at our Annual Meeting of Stockholders to be held on July 3, 2025, at 10:00 a.m. Mountain Time, and at any continuation, postponement, or adjournment of the Annual Meeting. The Annual Meeting will be held virtually via live webcast. You will be able to attend the Annual Meeting online by visitingwww.proxydocs.com/ICU and entering your 12-digit control number included on your proxy card or on the instructions that accompanied your proxy materials. You will be able to vote your shares electronically and submit your written questions prior to and during the meeting through the online website.

Holders of record of our Common Stock, par value $0.0001 per share, as of the close of business on May 5, 2025 (the “Record Date”), will be entitled to notice of and to vote at the Annual Meeting and at any continuation, postponement, or adjournment of the Annual Meeting. As of the Record Date, there were 10,494,639 shares of Common Stock outstanding and entitled to vote at the Annual Meeting. Each share of Common Stock is entitled to one vote on any matter presented to stockholders at the Annual Meeting.

The Company will begin mailing, or otherwise make available to stockholders, this Proxy Statement, Notice of Annual Meeting of Stockholders, and proxy card (the “Proxy Materials”) containing instructions on how to access the Proxy Materials and how to vote and the Company’s Annual Report on Form 10-K for the year ended December 31, 2024 (the “2024 Annual Report”) to stockholders on or about May 21, 2025. In this Proxy Statement, “Company”, “we”, “us”, and “our” refer to SeaStar Medical Holding Corporation.

EXPLANATORY NOTE

On June 7, 2024, we effected a 1-for-25 reverse stock split of our issued and outstanding common stock. Except as otherwise indicated, all common stock shares, common stock per share data, common stock options, and warrants in this proxy statement, including the exercise price of any common stock options, have been retrospectively adjusted to reflect the effect of the reverse stock split.

When and where will the Annual Meeting be held?

The Annual Meeting will be held on Thursday, July 3, 2025 at 10:00 a.m., Mountain Time. The Annual Meeting will be a completely virtual meeting, which will be conducted via live webcast. You will be able to attend the Annual Meeting online and submit your questions during the meeting by visitingwww.proxydocs.com/ICU and entering your 12-digit control number included in your Notice of Internet Availability of Proxy Materials, on your proxy card or on the instructions that accompanied your Proxy Materials. If you lose your 12-digit control number, you may join the Annual Meeting as a “Guest” but you will not be able to vote.

Availability of Proxy Materials

The Proxy Materials are being mailed on or about May 21, 2025 to all stockholders entitled to notice of, and to vote at, the Annual Meeting. SeaStar Medical Holding Corporation’s 2024 Annual Report, which includes its Form 10-K for the year ended December 31, 2024, will accompany the Proxy Materials.

Proposals

At the Annual Meeting, our stockholders will be asked:

• to elect two Class III Directors to serve until the 2028 annual meeting of stockholders, or until their successors shall have been duly elected and qualified;

• to approve an amendment and restatement of the Company’s 2022 Omnibus Equity Incentive Plan to (i) increase the number of authorized shares of Common Stock from 570,457, as adjusted for a 1-for-25 reverse stock split, to 2,070,457 and (ii) remove the evergreen provision;

• to approve, in accordance with applicable rules of the Nasdaq Stock Market, the potential future sale and issuance of shares of our common stock to Lincoln Park in accordance with the Lincoln Park Purchase Agreement that would result in Lincoln Park owning in excess of 19.99% of the shares of our common stock outstanding immediately after giving effect to such sale;

• to ratify the appointment of WithumSmith+Brown, PC as our independent registered public accounting firm for the fiscal year ending December 31, 2025; and

• to approve a proposal to adjourn or postpone the Annual Meeting to a later date or dates, if necessary, to permit further solicitation and vote of proxies if there are insufficient votes for, or otherwise in connection with, any of the proposals described above.

We know of no other business that will be presented at the Annual Meeting. If any other matter properly comes before the stockholders for a vote at the Annual Meeting, however, the proxy holders named on the Company’s proxy card will vote your shares in accordance with their best judgment.

Recommendations of the Board

The Board of Directors (the “Board”) recommends that you vote your shares as indicated below. If you return a properly completed proxy card, or vote your shares by telephone or Internet, your shares of common stock will be voted on your behalf as you direct. If not otherwise specified, the shares of Common Stock represented by the proxies will be voted, and the Board recommends that you vote:

• FOR the election of Eric Schlorff and Kenneth Van Heel as Class III Directors;

• FOR the approval of an amendment and restatement of the Company’s 2022 Omnibus Equity Incentive Plan to (i) increase the number of authorized shares of Common Stock from 570,457, as adjusted for a 1-for-25 reverse stock split, to 2,070,457 and (ii) remove the evergreen provision;

• FOR the approval, for purposes of complying with applicable rules of the Nasdaq Stock Market, the potential future sale and issuance of shares of our common stock to Lincoln Park in accordance with the Lincoln Park Purchase Agreement that would result in Lincoln Park owning in excess of 19.99% of the shares of our common stock outstanding immediately after giving effect to such sale;

• FOR the ratification of the appointment of WithumSmith+Brown, PC as our independent registered public accounting firm for the fiscal year ending December 31, 2025; and

• FOR the proposal to adjourn or postpone the Annual Meeting to a later date or dates, if necessary, to permit further solicitation and vote of proxies if there are insufficient votes for, or otherwise in connection with, any of the proposals described above.

If any other matter properly comes before the stockholders for a vote at the Annual Meeting, the proxy holders named on the Company’s proxy card will vote your shares in accordance with their best judgment.

Information About This Proxy Statement

Why you received this Proxy Statement. You are viewing or have received these Proxy Materials because our Board is soliciting your proxy to vote your shares at the Annual Meeting. This Proxy Statement includes information that we are required to provide to you under the rules of the Securities and Exchange Commission (“SEC”) and that is designed to assist you in voting your shares.

Printed Copies of Our Proxy Materials. You have received or will receive printed copies of our Proxy Materials, and instructions regarding how you can vote are contained on the proxy card included in the materials.

Householding. The SEC’s rules permit us to deliver a single set of Proxy Materials to one address shared by two or more of our stockholders. This delivery method is referred to as “householding” and can result in significant cost savings. To take advantage of this opportunity, we have delivered only one set of Proxy Materials to multiple stockholders who share an address, unless we received contrary instructions from the impacted stockholders prior to the mailing date. We agree to deliver promptly, upon written or oral request, a separate copy of the Proxy Materials, as requested, to any stockholder at the shared address to which a single copy of those documents was delivered. If you prefer to receive separate copies of the Proxy Materials, contact Continental Stock Transfer and Trust Company at 1-800-509-8856 or in writing at Continental Stock Transfer and Trust, 1 State Street 30 th Floor, New York, NY 10004-1561.

If you are currently a stockholder sharing an address with another stockholder and wish to receive only one copy of future proxy materials for your household, contact Continental Stock Transfer and Trust Company at 1-800-509-8856 or in writing at Continental Stock Transfer and Trust, 1 State Street 30 th Floor, New York, NY 10004-1561.