Exhibit 5.1

ArentFox Schiff LLP   1717 K Street NW Washing, DC 20006 202.857.6000       main 202.857.6395       fax   afslaw.com

February 17, 2026

Board of Directors
626 Bancroft Way
Suite A
Berkeley, CA 94710

Ladies and Gentlemen:

We have acted as counsel to Profusa, Inc., a Delaware corporation (the “Company”), in connection with the preparation and filing with the Securities and Exchange Commission (the “Commission”) of the Company’s Registration Statement on Form S-1 (the “Registration Statement”) under the Securities Act of 1933 (the “Act”). The Registration Statement relates to, among other things, the direct offer and sale of (i) up to 126,500 shares of common stock of the Company, par value $0.0001 per share (the “Common Stock”) issuable upon the exercise of 9,487,500 warrants of the Company (the “Public Warrants,” and upon exercise the “Public Warrant Shares”), each initially exercisable for one seventy-fifth (1/75) of one share at an exercise price of $862.50 per whole share, and (ii) up to 97,966 shares of Common Stock that are issuable upon the exercise of 7,347,500 private placement warrants of the Company (the “Private Placement Warrants,” and upon exercise the “Private Warrant Shares”), each initially exercisable for one seventy-fifth (1/75) of one share at an exercise price of $862.50 per whole share, issued to the Sponsor, I-Bankers Securities, Inc., and Dawson James Securities, Inc., in connection with the Company’s initial public offering.

In connection with our opinion, we have examined (i) the Third Amended and Restated Articles of Incorporation of the Company in the form filed as Exhibit 3.1 to the Registration Statement, as filed with the Secretary of State of the State of Delaware on April 30, 2018; (ii) the Bylaws of the Company in the form filed as Exhibit 3.3 to the Registration Statement, as filed with the Commission on June 16, 2021; (iii) the Purchase Agreement; (iv) the Registration Rights Agreement, between the Company and the Selling Stockholder dated as of July 11, 2025 (the “Registration Rights Agreement”) in the form filed as Exhibit 10.20 to the Registration Statement; (v) the Subscription Agreement; (vi) the Warrant Purchase Agreement; (vii) the Short-Term Bridge Loans; (viii) the Registration Statement, including the exhibits thereto, and such other documents, corporate records and instruments, and have examined such laws and regulations, as we have deemed necessary for the purposes of this opinion. In making our examination, we have assumed the genuineness of all signatures, the authenticity of all documents submitted to us as originals, the conformity with the originals of all documents submitted to us as copies and the legal capacity of all natural persons. As to matters of fact material to our opinions in this letter, we have relied on certificates and statements from officers and other employees of the Company, public officials and other appropriate persons.

February 17, 2026 Page 2

Based on the foregoing and subject to the qualifications set forth below, we are of the opinion that:

The foregoing opinions are limited to the General Corporation Law of Delaware, including all Delaware statutes and all Delaware court decisions that affect the interpretation of such General Corporation Law, as of the date hereof. This opinion is rendered pursuant to Item 601(b)(5)(i) of Regulation S-K under the Act.

The opinions expressed in this opinion letter are as of the date of this opinion letter only and as to laws covered hereby only as they are in effect on that date, and we assume no obligation to update or supplement such opinions to reflect any facts or circumstances that may come to our attention after that date or any changes in law that may occur or become effective after that date. The opinions herein are limited to the matters expressly set forth in this opinion letter, and no opinion or representation is given or may be inferred beyond the opinions expressly set forth in this opinion letter.

We hereby consent to the filing of this opinion with the Commission as an exhibit to the Registration Statement and to the use of this firm’s name under the caption “Legal Matters” in the Registration Statement. In giving this consent, we do not thereby admit that we are within the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission promulgated thereunder.