Exhibit 5.1

Wilson Sonsini Goodrich & Rosati
Professional Corporation   650 Page Mill Road
Palo Alto, California 94304-1050   O: 650.493.9300 F: 650.493.6811

March 9, 2023

ALX Oncology Holdings Inc.

323 Allerton Avenue

South San Francisco, California 94080

Re: Registration Statement on Form S-8

Ladies and Gentlemen:

We have examined the Registration Statement on Form S-8 (the “Registration Statement”) to be filed by ALX Oncology Holdings Inc., a Delaware corporation (the “Company”), with the Securities and Exchange Commission on or about the date hereof, relating to the registration under the Securities Act of 1933, as amended, of 1,634,456 shares of common stock, par value $0.001 per share (the “Common Stock”), reserved for issuance pursuant to the Company’s Amended and Restated 2020 Equity Incentive Plan (which plan is referred to herein as the “Plan” and which shares of Common Stock are referred to herein as the “Shares”).

On the basis of the foregoing, and in reliance thereon, we are of the opinion that the Shares, when issued and sold in the manner referred to in the Plan and pursuant to the agreements that accompany the Plan, will be legally and validly issued, fully paid, and nonassessable.

We consent to the use of this opinion as an exhibit to the Registration Statement and further consent to the use of our name wherever appearing in the Registration Statement and any amendments thereto.

Very truly yours,

WILSON SONSINI GOODRICH & ROSATI

Professional Corporation

/s/ Wilson Sonsini Goodrich & Rosati, P.C.