EX-5.1

Exhibit 5.1

January 11, 2019

Keane Group, Inc.

1800 Post Oak Blvd Suite 450

Houston, TX 77056

Ladies and Gentlemen:

We have acted as counsel to Keane Group, Inc., a Delaware corporation (the “Company”), in connection with the preparation and filing by the Company with the Securities and Exchange Commission (the “Commission”) of a Registration Statement on Form S-3 (File No. 333-222831) (the “Registration Statement”), under the Securities Act of 1933, as amended (the “Securities Act”), relating to an aggregate of 51,668,175 shares of the Company’s common stock, par value $0.01 per share, that may be sold from time to time by certain selling stockholders (the “Selling Stockholder Shares”). The Selling Stockholder Shares may be offered and sold from time to time pursuant to the plan of distribution set forth in the Prospectus (as defined herein).

In connection with the opinions expressed below, we have examined originals or copies, certified or otherwise identified to our satisfaction, of the Registration Statement, the Company’s prospectus dated February 2, 2018 (the “Base Prospectus”), as supplemented by the Company’s prospectus supplement, dated January 11, 2019 (together with the Base Prospectus, the “Prospectus”), filed by the Company pursuant to Rule 424(b) of the rules and regulations of the Commission under the Securities Act, and the Certificate of Incorporation and Bylaws of the Company, both of which were filed with the Commission on March 21, 2017 as exhibits to Company’s Annual Report on Form 10-K and have been incorporated by reference as exhibits to the Registration Statement, and such other agreements, certificates and documents of public officials, officers and other representatives of the Company and others as we have deemed necessary as a basis for our opinions set forth below.

In our examination, we have assumed (a) the legal capacity of all natural persons executing the Registration Statement, and such other agreements, certificates and documents, (b) the genuineness of all signatures thereon, (c) the authority of all persons signing the Registration Statement and such other agreements, certificates and documents on behalf of the parties thereto, (d) the authenticity of all documents submitted to us as originals, (e) the conformity to original documents of all documents submitted to us as certified or photostatic copies and (f) the authenticity of the originals of such latter documents. As to any facts material to this opinion that were not independently established or verified, we have relied upon statements and representations of officers and other representatives of the Company and others.