EX-5.1

Exhibit 5.1

650 Page Mill Road

Palo Alto, CA 94304-1050

PHONE 650.493.9300

FAX 650.493.6811

www.wsgr.com

March 20, 2019

Box, Inc.

900 Jefferson Ave.

Redwood City, CA 94063

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 Box, Inc., a Delaware corporation, with the Securities and Exchange Commission on or about the date hereof, in connection with the registration under the Securities Act of 1933, as amended, of an aggregate of 8,658,644 shares of Class A common stock, par value $0.0001 per share, consisting of: (i) 7,215,537 shares of Class A common stock reserved for issuance under the 2015 Equity Incentive Plan and (ii) 1,443,107 shares of Class A common stock reserved for issuance under the 2015 Employee Stock Purchase Plan (which plans are referred to herein as the “Plans” and which shares of Class A common stock are collectively 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 Plans and pursuant to the agreements that accompany the Plans, 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.