The company, which specializes in turning around troubled companies, expanded by about 22,000 square feet at the 26-story building at the corner of East 58th Street, sources told The Real Deal.
Financial terms of the deal were not immediately available.
Representatives for Alvarez & Marsal and Ruben Companies could not be immediately reached for comment. David Dusek and Mitchell Konsker at JLL negotiated the expansion on behalf of the tenant. The brokers declined to comment.
Ruben Companies paid $210 million in 2013 to buy the fee position at 600 Madison Avenue, where the investor had held the leasehold on the building since the 1970s.
The owner refinanced the property earlier this year with a $185 million loan from Prudential Insurance, property records show.