Two new leases have been signed by long-term tenants at 257 Park Ave. South, also known as the Gramercy Park Building, with The Feil Organization.

Madison Logic has doubled the size of its New York City corporate headquarters for an overall total of 24,562 square feet. Madison Logic, a data solutions provider for B2B advertisers, has been a tenant since 2000.

Environmental Defense Fund, a national nonprofit organization, has signed a renewal for 44,010 square feet for its headquarters. The fund has been a tenant at 257 Park Ave. South since 1996.

Built in 1912, the 20-story, 226,000-square-foot class-B Midtown South building, at 21st Street, is near Madison Square Park and Union Square Park.

Robert Griffitts, a partner at Griffitts O’Hara, represented Madison Logic.

Gregg Bucci, a partner at Wilson Elser Moskowitz Edleman & Dicker in White Plains, represented the Environmental Defense Fund.

Brian Palumbo and Michele Frankel were in-house counsel for Feil.

The asking rate at 257 Park Ave. South is in the low $60s per square foot and the occupancy rate is about 97 percent.

Madison, which partners with more than 300 B2B publishers, has offices in San Francisco and London.

Since its start in 1967, the Environmental Defense Fund has sought to preserve natural systems through innovations to protect the environment and through the creation of transformational solutions to address serious environmental problems, according its website. It has nine offices in the United States, including Washington, D.C., San Francisco and Boston, plus two international offices in Beijing, China, and La Paz, Mexico.

Feil operates a nationwide portfolio of more than 26 million square feet of retail and commercial space and over 5,000 residential rental units.

Feil’s Robert Fisher, director of commercial leasing, and Brian Feil, vice president of leasing, handled the leases in-house for the landlord.

Marc Ellman, president and owner of Ellman Realty Advisors, handled the lease for Madison Logic.

Alan Desino, an executive managing director at Colliers International, acted on behalf of the Environmental Defense Fund.