Exhibit 5.1

January 20, 2010

SL Green Realty Corp.

420 Lexington Avenue

New York, New York 10170

Re:   Registration Statement on Form S-3

Ladies and Gentlemen:

We have served as Maryland counsel to SL Green Realty Corp., a Maryland corporation (the “Company”), in connection with certain matters of Maryland law arising out of the registration of 5,400,000 shares of the Company’s 7.625% Series C Cumulative Redeemable Preferred Stock, $.01 par value per share (the “Shares”), to be issued and sold in a public offering.  The Shares are covered by the above-referenced Registration Statement and all amendments thereto,  filed by the Company with the Securities and Exchange Commission (the “Commission”) pursuant to the Securities Act of 1933, as amended (the “1933 Act”).

In connection with our representation of the Company, and as a basis for the opinion hereinafter set forth, we have examined originals, or copies certified or otherwise identified to our satisfaction, of the following documents (hereinafter collectively referred to as the “Documents”):

1.                                       The Registration Statement (Registration No. 333-68493), including all amendments thereto, with the prospectus included therein, in the form in which it was transmitted to the Commission under the 1933 Act,

2.                                       The charter of the Company (the “Charter”), certified by the State Department of Assessments and Taxation of Maryland (the “SDAT”);

3.                                       The Second Amended and Restated Bylaws of the Company, as amended by Amendment #1 and Amendment #2, certified as of the date hereof by an officer of the Company;

4.                                       Resolutions adopted by the Board of Directors of the Company (the “Resolutions”) relating to the registration, sale and issuance of the Shares, certified as of the date hereof by an officer of the Company;

5.                                       A certificate of the SDAT as to the good standing of the Company, dated as of a recent date;

6.                                       A certificate executed by an officer of the Company, dated as of the date hereof; and

7.                                       Such other documents and matters as we have deemed necessary or appropriate to express the opinion set forth below, subject to the assumptions, limitations and qualifications stated herein.

In expressing the opinion set forth below, we have assumed the following:

1.                                       Each individual executing any of the Documents, whether on behalf of such individual or another person, is legally competent to do so.

2.                                       Each individual executing any of the Documents on behalf of a party (other than the Company) is duly authorized to do so.

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3.                                       Each of the parties (other than the Company) executing any of the Documents has duly and validly executed and delivered each of the Documents to which such party is a signatory, and such party’s obligations set forth therein are legal, valid and binding and are enforceable in accordance with all stated terms.

4.                                       All Documents submitted to us as originals are authentic.  The form and content of all Documents submitted to us as unexecuted drafts do not differ in any respect relevant to this opinion from the form and content of such Documents as executed and delivered.  All Documents submitted to us as certified or photostatic copies conform to the original documents.  All signatures on all such Documents are genuine.  All public records reviewed or relied upon by us or on our behalf are true and complete.  All representations, warranties, statements and information contained in the Documents are true and complete.  There has been no oral or written modification of or amendment to any of the Documents, and there has been no waiver of any provision of any of the Documents, by action or omission of the parties or otherwise.

5.                                       None of the Shares will be issued, sold or transferred in violation of the restrictions on ownership and transfer contained in the Charter.

Based upon the foregoing, and subject to the assumptions, limitations and qualifications stated herein, it is our opinion that:

1.                                       The Company is a corporation, duly incorporated and existing under and by virtue of the laws of the State of Maryland and is in good standing with the SDAT.

2.                                       The Shares have been duly authorized and, when and if issued against payment therefor in accordance with the Resolutions and the Registration Statement, will be validly issued, fully paid and nonassessable.

The foregoing opinion is limited to the laws of the State of Maryland and we do not express any opinion herein concerning any other law.  We express no opinion as to compliance with any federal or state securities laws, including the securities laws of the State of Maryland.  We assume no obligation to supplement this opinion if any applicable law changes after the date hereof or if we become aware of any fact that might change the opinion expressed herein after the date hereof.

This opinion is being furnished to you for submission to the Commission as an exhibit to the Company’s Current Report on Form 8-K relating to the issuance of the Shares (the “Current Report”), which is incorporated by reference in the Registration Statement.

We hereby consent to the filing of this opinion as an exhibit to the Current Report and the said incorporation by reference and to the use of the name of our firm therein.  In giving this consent, we do not admit that we are within the category of persons whose consent is required by Section 7 of the 1933 Act.

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