Exhibit 5.1

March 26, 2013

StoneMor Partners L.P.

311 Veterans Highway, Suite B

Levittown, PA 19056

Ladies and Gentlemen:

We have acted as counsel to StoneMor Partners L.P., a Delaware limited partnership (the “Partnership”), in connection with the proposed offer and sale by the Partnership of up to 1,610,000 common units (including an option to purchase up to 210,000 additional common units to cover over-allotments) representing limited partner interests of the Partnership (the “Offered Units”) pursuant to an underwriting agreement dated March 21, 2013 (the “Underwriting Agreement”), among the Partnership, StoneMor GP LLC, a Delaware limited liability company (the “General Partner”), StoneMor Operating Company LLC, a Delaware limited liability company, and Raymond James & Associates, Inc., as representative for the underwriters named therein (the “Underwriters”).

We refer to the Registration Statement on Form S-3 (Registration No. 333-170870), as amended, filed by the Partnership with the Securities and Exchange Commission (the “Commission”) pursuant to the Securities Act of 1933, as amended (the “Securities Act”), which was declared effective by the Commission on December 15, 2010 (the “Registration Statement”) and included a base prospectus (the “Base Prospectus”) and a prospectus supplement, dated March 21, 2013 (the “Prospectus Supplement”). The Base Prospectus, together with the Prospectus Supplement, is referred to herein as the “Prospectus.”

In rendering the opinions set forth below, we have examined originals or copies, certified or otherwise identified to our satisfaction, of (i) the Registration Statement, (ii) the Prospectus, (iii) the certificate of limited partnership of the Partnership, (iv) the Second Amended and Restated Agreement of Limited Partnership of the Partnership, dated as of September 9, 2008 (the “Partnership Agreement”), (v) resolutions of the board of directors of the General Partner, the pricing committee of the board of directors of the General Partner and the board of directors of StoneMor Operating LLC, (vi) the Underwriting Agreement and (vii) such other certificates, statutes, including the Delaware Revised Uniform Limited Partnership Act (the “Delaware LP Act”), and other instruments and documents as we considered appropriate for purposes of the opinions hereafter expressed. In addition, we reviewed such questions of law as we considered appropriate.

Based on the foregoing, and subject to the assumptions, limitations and qualifications set forth herein, we are of the opinion that the Offered Units, when issued and delivered against payment therefor in accordance with the terms of the Underwriting Agreement, will be validly issued, fully paid (to the extent required by the Partnership Agreement) and non-assessable, except as such nonassessability may be affected by Sections 17-303, 17-607 and 17-804 of the Delaware LP Act and as described in the Prospectus.

The opinions expressed herein are qualified in the following respects:

We hereby consent to the filing of this opinion of counsel as Exhibit 5.1 to the Current Report on Form 8-K of the Partnership dated on or about the date hereof, to the incorporation by reference of this opinion of counsel into the Registration Statement and to the reference to our firm under the heading “Legal Matters” in the Prospectus. By giving such consent, we do not admit that we are within the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission issued thereunder.