Ryan Sansom T +1 617 937 2335 rsansom@cooley.com EXHIBIT 5.1

November 3, 2022

Acrivon Therapeutics, Inc.

480 Arsenal Way, Suite 100

Watertown, Massachusetts 02472

Ladies and Gentlemen:

You have requested our opinion, as counsel to Acrivon Therapeutics, Inc., a Delaware corporation (the “Company”), in connection with the filing by the Company of a Registration Statement (No. 333-267911) on Form S-1 (the “Registration Statement”) with the Securities and Exchange Commission, including a related prospectus included in the Registration Statement (the “Prospectus”), covering an underwritten public offering of up to 6,785,000 shares (the “Shares”) of the Company’s common stock, par value $0.001, including up to 885,000 Shares that may be sold pursuant to the exercise of an option to purchase additional shares.

In connection with this opinion, we have (i) examined and relied upon (a) the Registration Statement and the Prospectus, (b) the Company’s Second Amended and Restated Certificate of Incorporation and Bylaws, each as currently in effect, (c) the Company’s Amended and Restated Certificate of Incorporation, filed as Exhibit 3.3 to the Registration Statement, and the Company’s Amended and Restated Bylaws, filed as Exhibit 3.4 to the Registration Statement, each of which is to be in effect immediately following the closing of the offering contemplated by the Registration Statement and (d) originals or copies certified to our satisfaction of such records, documents, certificates, memoranda and other instruments as in our judgment are necessary or appropriate to enable us to render the opinion expressed below and (ii) assumed that the Shares to be sold to the underwriters by the Company will be sold at a price established by the Board of Directors of the Company or a duly authorized committee thereof.

We have assumed the genuineness of all signatures, the authenticity of all documents submitted to us as originals, the conformity to originals of all documents submitted to us as copies, the accuracy, completeness and authenticity of certificates of public officials and the due authorization, execution and delivery of all documents by all persons other than the Company where authorization, execution and delivery are prerequisites to the effectiveness thereof. As to certain factual matters, we have relied upon a certificate of an officer of the Company and have not independently verified such matters.

Our opinion is expressed only with respect to the General Corporation Law of the State of Delaware. We express no opinion as to whether the laws of any particular jurisdiction are applicable to the subject matter hereof. We are not rendering any opinion as to compliance with any federal or state law, rule or regulation relating to securities, or to the sale or issuance thereof.

On the basis of the foregoing, and in reliance thereon, we are of the opinion that the Shares, when sold and issued against payment therefor as described in the Registration Statement and the Prospectus, will be validly issued, fully paid and non-assessable.

Cooley LLP    500 Boylston St    Boston, MA    02116-3736

t: (617) 937-2300 f: (617) 937-2400 cooley.com

Acrivon Therapeutics, Inc.

Page 2

We consent to the reference to our firm under the caption “Legal Matters” in the Prospectus included in the Registration Statement and to the filing of this opinion as an exhibit to the Registration Statement.

Sincerely,
Cooley LLP
By:	/s/ Ryan Sansom
	Ryan Sansom

Cooley LLP    500 Boylston St    Boston, MA    02116-3736

t: (617) 937-2300 f: (617) 937-2400 cooley.com