Law Firm Simpson Thacher Set to Lease 700K SF at 570 Fifth Avenue

Global law firm Simpson Thacher & Bartlett is getting ready to sign a massive deal at a new office skyscraper in Midtown, Commercial Observer has learned.

Simpson Thacher, which provides counsel in corporate transactions, private equity, capital markets, banking and litigation, is set to lease roughly 700,000 square feet at Extell Development’s office development at 570 Fifth Avenue, according to sources with knowledge of the deal.

It’s unclear whether the deal represents a relocation or an additional location for the law firm, which currently has its New York City offices at 425 Lexington Avenue, according to its website.

However, it seems Simpson Thacher has been trying to shed its space at its 425 Lexington spot, as the firm subleased nearly 60,000 square feet of its office space at the building to fellow law firm Holwell Shuster & Goldberg in June 2017, as CO previously reported.

The length of Simpson Thacher’s new lease at 570 Fifth and the asking rent were unclear, but a report from Newmark found office rents in Midtown averaged $79.84 per square foot during the second quarter of 2025.

Spokespeople for Simpson Thacher and Extell did not immediately respond to requests for comment.

Led by Gary Barnett, Extell plans to build a 29-story office and retail building anchored by Ikea at the Fifth Avenue address, with completion projected by the end of 2028. In March, Extell bought the empty lot at 576 Fifth Avenue for $175 million to secure the last portion of land needed for the project.

Once approved, Simpson Thacher’s deal at the new building between West 46th and West 47th streets would mark one of the largest office leases completed so far this year, second only to New York University’s 1.08 million-square-foot lease at 770 Broadway in May.

That was followed by Amazon’s deal for 330,000 square feet at 10 Bryant Park in April, and law firm Goodwin Procter’s lease for 250,000 square feet at 200 Fifth Avenue, also in April.

News of the potential deal also follows the strongest first half for law firm leasing in the U.S. since 2018, according to a report from Savills. During the first half of 2025, 5.9 million square feet of law firm leases exceeding 20,000 square feet were signed across the country, the highest first-half volume since 2018.

Isabelle Durso can be reached at idurso@commercialobserver.com.