Exhibit 5.1

Carlton Fleming

+1 650 843 5865

cfleming@cooley.com

September 11, 2018

DocuSign, Inc.

221 Main St., Suite 1000

San Francisco, CA 94105

Ladies and Gentlemen:

We have acted as counsel to DocuSign, Inc., a Delaware corporation (the “Company”), in connection with the filing by the Company of a Registration Statement on Form S-1 (the “Registration Statement”) with the Securities and Exchange Commission, including a related prospectus filed with the Registration Statement (the “Prospectus”), covering an underwritten public offering of up to 9,269,632 shares of the Company’s common stock (the “Shares”), par value $0.0001 per share, to be sold by the selling stockholders identified in such Registration Statement (including up to 1,209,082 Shares that may be sold pursuant to the exercise of an over-allotment option to be granted to the underwriters) (collectively, “Stockholder Shares”).

In connection with this opinion, we have examined and relied upon (a) the Registration Statement and the Prospectus, (b) the Company’s Amended and Restated Certificate of Incorporation and Bylaws, each as amended and in effect as of the date hereof, and (c) 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.

We have assumed the genuineness and authenticity of all documents submitted to us as originals and the conformity to originals of all documents submitted to us as copies and the due execution and delivery, other than by the Company, of all documents where due execution and delivery are a prerequisite to the effectiveness thereof. As to certain factual matters, we have relied upon a certificate of an officer of the Company and have not sought independently to verify such matters.

Our opinion is expressed only with respect to the General Corporation Law of the State of Delaware. We express no opinion to the extent that any other laws are applicable to the subject matter hereof and no opinion and provide no assurance as to compliance with any federal or state securities law, rule or regulation.

On the basis of the foregoing, and in reliance thereon, we are of the opinion that the Stockholder Shares have been validly issued and are fully paid and non-assessable.

Cooley LLP    3175 Hanover Street    Palo Alto, CA    94304-1130

t: (650) 843-5000 f: (650) 849-7400 cooley.com

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/ Carlton Fleming
	Carlton Fleming

Cooley LLP    3175 Hanover Street    Palo Alto, CA    94304-1130

t: (650) 843-5000 f: (650) 849-7400 cooley.com