ICU SeaStar Medical Holding Corporation

Prospectus Supplement No. 11

Filed Pursuant to Rule 424(b)(3)

File No. 333-268503

SeaStar Medical Holding Corporation

3513 Brighton Blvd,

Suite 410

Denver, CO 80216

(844) 427-8100

Prospectus Supplement No. 11

(to the Prospectus dated January 4, 2023)

This Prospectus Supplement No. 11 supplements and amends the prospectus dated January 4, 2023, as amended by Prospectus Supplement No. 1 dated February 15, 2023, Prospectus Supplement No. 2 dated February 16, 2023, Prospectus Supplement No. 3 dated March 16, 2023, Prospectus Supplement No. 4 dated March 31, 2023, Prospectus Supplement No. 5 dated March 31, 2023, Prospectus Supplement No. 6 dated May 10, 2023, Prospectus Supplement No. 7 dated May 19, 2023, Prospectus Supplement No. 8 dated May 23, 2023, Prospectus Supplement No. 9 dated June 12, 2023, and Prospectus Supplement No. 10 dated June 21, 2023 (the “Prospectus”), relating to the sale from time to time of up to 9,829,000 shares of our common stock and 6,438,000 of our warrants to purchase common stock by a selling shareholder.

On June 30, 2023, we filed with the U.S. Securities and Exchange Commission the attached Current Report on Form 8-K.

This Prospectus Supplement No. 11 should be read in conjunction with the Prospectus and is qualified by reference to the Prospectus except to the extent that the information in this Prospectus Supplement No. 11 supersedes the information contained in the Prospectus.

Our common stock is traded on the Nasdaq Stock Market under the symbol “ICU”. On July 3, 2023, the last reported sale price of our common stock was $0.52 per share.

Investing in our common stock involves a high degree of risk. See “Risk Factors” beginning on page 6 of the Prospectus dated January 4, 2023.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this Prospectus Supplement No. 11 is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this Prospectus Supplement No. 11 is July 5, 2023.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): June 26, 2023

SeaStar Medical Holding Corporation

(Exact name of Registrant as Specified in Its Charter)

Registrant’s Telephone Number, Including Area Code: (844) 427-8100

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company  ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.  ☐

Item 3.01 Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing.

On June 26, 2023, SeaStar Medical Holding Corporation (the “Company”) received a deficiency letter from the Listing Qualifications Department (the “Staff”) of the Nasdaq Stock Market (“Nasdaq”) notifying the Company that, for the preceding 30 consecutive business days, the closing bid price for the Company’s common stock, par value $0.0001 per share (the “Common Stock”) was below the minimum $1.00 per share requirement for continued inclusion on The Nasdaq Capital Market pursuant to Nasdaq Listing Rule 5550(a)(2) (the “Bid Price Requirement”).

The notification received has no immediate effect on the Company’s Nasdaq listing. In accordance with Nasdaq rules, the Company has been provided an initial period of 180 calendar days, or until December 26, 2023 (the “Compliance Date”), to regain compliance with the Bid Price Requirement. If, at any time before the Compliance Date, the closing bid price for the Common Stock is at least $1.00 for a minimum of 10 consecutive business days, the Staff will provide the Company written confirmation of compliance with the Bid Price Requirement.

The Company intends to monitor the closing bid price of the Common Stock and may, if appropriate, consider available options to regain compliance with the Bid Price Requirement.

Item 5.07 Submission of Matters to a Vote of Security Holders.

The annual meeting of stockholders of the Company was held virtually on June 28, 2023 at 10:00 a.m., Mountain Time. The following proposals were approved by the stockholders, each by the votes set forth below:

Proposal 1. To elect two Class I Directors to serve until the 2026 annual meeting of stockholders, or until their successors shall have been duly elected and qualified.

Proposal 2. To approve, for purposes of complying with Nasdaq Listing Rule 5635(d), the full issuance of shares of Common Stock issuable by the Company pursuant to the Convertible Notes (as defined in the proxy statement) and the Warrants (as defined in the proxy statement).

Proposal 3. To approve, for purposes of complying with Nasdaq Listing Rule 5635(d), the full issuance of shares of Common Stock issuable by the Company pursuant to the Company’s Equity Line of Credit (as defined in the proxy statement).

Proposal 4. To ratify the appointment of Armanino LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2023.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.