SL Green Realty Corp. — Manhattan’s largest office landlord — has agreed to acquire Park Avenue Tower for $730 million in one of New York City’s biggest office trades of the year so far.

The 36-story, 621,824-square-foot, Class A tower at 65 E. 55th St. sits in the Plaza District. Designed by Helmut Jahn and completed in 1986, the building has benefited from major renovations throughout the last decade, including a new lobby, upgraded plaza and high-end, pre-built suites.

SL Green moved quickly to secure the asset, preempting other bids once Blackstone brought it to market. The deal is expected to close in early 2026. Eastdil Secured represented the seller.

Blackstone exits at a slight discount to its 2014 acquisition price of $750 million and below the estimated $925 million it has invested in total. Even so, the sale allows the firm to complete the wind-down of a fund that is 95% realized, delivering a 14% internal rate of return.

Park Avenue Tower is well-leased at below-market rents, giving SL Green immediate cash flow and upside as leases roll. Tenants include PineBridge Investments (75,000 square feet); investment bank BTIG; Raine Group; Quilvest Capital Partners; Panagram Structured Asset Management; and Reinsurance Group of America, which signed a 17,458-square-foot lease in August for its first New York office.

Along Park Avenue, SL Green already controls One Vanderbilt, 500 Park Ave., 450 Park Ave., 280 Park Ave., 245 Park Ave., 125 Park Ave. and 100 Park Ave. The company also recently acquired 346 Madison Ave. and 11 E. 44th St. for $160 million.

Chief Investment Officer, Harrison Sitomer, called the tower “an exceptional property in a corridor where demand has never been higher,” noting the combination of sustainable cash flow, below-market rents and long-term value creation.

The deal comes as Manhattan’s office market shows its strongest recovery in two decades. Leasing reached the largest amount of office space rented through Q3 of any year since 2022.

Manhattan was also the first U.S. city to surpass pre-pandemic office foot traffic after closing the return-to-office gap by mid-2025. Investment activity echoes that impetus: RXR’s $1.08 billion purchase of 590 Madison Ave. (Tishman Speyer’s first New York office buy since 2019) and Amazon’s return to Midtown acquisitions all point toward renewed demand for high-quality assets.

International investors remain active, too. For example, Japan’s Mori Building recently increased its stake in SL Green’s One Vanderbilt in a vote of global confidence in Manhattan’s premium office market, especially sustainable, transit-adjacent towers.