UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K/A

(Amendment No. 1)

For the fiscal year ended December 31, 2014

For the transition period from                      to                     

Commission File Number: 001-36106

EMPIRE STATE REALTY OP, L.P.

(Exact name of Registrant as specified in its charter) 

One Grand Central Place, 60 East 42nd Street, New York, New York 10165

(Address of principal executive offices) (Zip Code)

(212) 687-8700

(Registrant’s telephone number, including area code)

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act:

None

Indicate by check mark if the Registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.    Yes  x    No  ¨

Indicate by check mark if the Registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act.    Yes  ¨    No  x

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.    Yes  x    No  ¨

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).    Yes  x    No  ¨

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of the registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K.  x

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer or a smaller reporting company. See definition of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act.

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).    Yes  ¨    No  x

As of February 23, 2015, there were 41,305,321 units of the Registrants’ Series ES operating partnership units outstanding, 11,293,105 units of the Series 60 operating partnership units outstanding, and 5,614,734 units of the Series 250 operating partnership units outstanding.

DOCUMENTS INCORPORATED BY REFERENCE

Our sole general partner is Empire State Realty Trust, Inc. Portions of the Empire State Realty Trust, Inc.’s Proxy Statement for its 2015 Annual Stockholders’ Meeting (which was held on June 17, 2015) filed on April 30, 2015 are incorporated by reference into Part III of our Annual Report on Form 10-K.

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Explanatory Note

This Amendment No. 1 amends the registrant’s Annual Report on Form 10-K for the fiscal year ended December 31, 2014 (the “Original Form 10-K”) solely for the purpose of filing updated officer certifications required by Section 302 of the Sarbanes-Oxley Act of 2002, in conformity with Item 601(b)(31)(i) of Regulation S-K, including certain required language from paragraph 4 that was inadvertently omitted from the versions of the certifications filed with the Original Form 10-K. In accordance with applicable Securities and Exchange Commission guidance, this Form 10-K/A contains only the cover page, this explanatory note, a signature page, and the revised officer certifications, which are filed as Exhibits 31.1 and 31.2 herewith.

Except as described above and except for Exhibits 31.1 and 31.2 filed herewith, the disclosures presented in the Original Form 10-K filed on February 27, 2015 have not been amended or updated and this report speaks only as of such filing date. Therefore, you should refer to the registrant’s Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and other reports subsequently filed with or furnished to the Securities and Exchange Commission for information about the registrant since February 27, 2015.

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PART IV

The exhibit index below lists the exhibits that are being filed with this Form 10-K/A.

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SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, as amended, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

EMPIRE STATE REALTY OP, L.P.

By: Empire State Realty Trust, Inc., its general partner

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Exhibit Index

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