SL Green, Mori Team Up on New Midtown Office Tower

SL Green is doubling down on Manhattan’s trophy office market, bringing in Japan’s Mori Building Co. to develop a new office tower steps from Grand Central Terminal.

The deal: SL Green Realty has partnered with Tokyo-based Mori Building Co. to build 346 Madison Avenue, a 46-story office tower in Midtown Manhattan. The project will deliver approximately 850,000 SF of rentable office space and further expands the two companies’ growing relationship in New York.

Project details: Designed by Kohn Pedersen Fox (KPF), the tower will feature premium amenities including outdoor terraces, a wellness center with a padel court, an auditorium, and a tenant lounge. The project will rise between 44th and 45th Streets near Grand Central Terminal, just steps from SL Green’s One Vanderbilt.

Capital commitment: SL Green acquired two adjacent buildings at the site for $160M in 2025 and plans to demolish them to make way for the new development. As part of the partnership, Mori purchased a 49% stake in the project at a gross valuation of $175M.

Building on a successful partnership: Mori has already invested alongside SL Green, acquiring stakes in One Vanderbilt through two transactions over the past two years, each valuing the tower at roughly $4.7 billion. The latest deal reinforces confidence in Manhattan’s top office assets.

Why now: Manhattan office leasing posted its strongest quarter since 2019 in early 2026, according to Savills, with demand concentrated in new and renovated trophy buildings. Reflecting that trend, SL Green’s One Vanderbilt and One Madison are both fully leased to finance and technology tenants.

➥ THE TAKEAWAY

Quality still wins: The project is another sign that the office market’s flight to quality remains firmly in place. As tenants gravitate toward newer, amenity-rich buildings, demand for premier space continues to outpace supply.

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