Cushman & Wakefield arranges 41,000 s/f lease at Rockrose’s 300 Park Ave. South

Manhattan, NY Cushman & Wakefield negotiated a 41,000 s/f lease at 300 Park Ave. South on behalf of the landlord, Rockrose Development. Flexible Finance Inc. (Flex) agreed to lease the top three floors of the 15-story building in Midtown South. The firm will relocate to the property from a nearby building this year.

Cushman & Wakefield’s Drew Braver, Matthias Li, Remy Liebersohn, Heather Thomas and Josh Kuriloff facilitated the off-market transaction on behalf of Rockrose, who was represented internally by director of commercial leasing Rob Fink. Tenant representation was provided by Ryan Alexander and Jared Isaacson of CBRE.

“This off-market transaction is a testament to the continued strength of the Park Avenue South corridor and the tech sector’s renewed confidence in the market,” said Braver. “300 Park Avenue South continues to stand out as one of the premier assets in the submarket.”

The lease with Flex brings the building to 90% occupancy after a successful year of leasing that includes transactions completed with AI company Basis for 13,671 s/f, and private equity firm TCG Capital, which leased 4,533 s/f at the building. Basis was represented by Mike Mathias and RJ Johns of Cushman & Wakefield, while TCG was represented by Simon Landmann and Matthew Astrachan of JLL.

In addition to the recent leasing activity, Rockrose and Cushman & Wakefield are bringing to market the entire fourth floor of the building, which features a pre-built office space designed by architect MKDA.

“Given the growing demand for turn-key space in Midtown South, we are anticipating strong interest for this high-end space on the fourth floor of 300 Park Avenue South,” said Li “We look forward to launching our lease-up efforts for the full floor in the coming weeks.”

Originally built in 1910, 300 Park Avenue South — also known as the Mills & Grubb Building — is a fully modernized, 200,000-square-foot office property that blends historic charm with contemporary functionality. Featuring an incredible shared roof deck amenity with sweeping views of Manhattan along the Park Avenue South corridor, high ceilings, large floor plates, and standout architectural details like arched windows, the building offers a strong branding opportunity in the heart of Midtown South. Located near Union Square and Madison Square Park, with a subway entrance at its doorstep, the property provides excellent access to dining, retail, and major transit hubs.