Leibman died on Friday.
Robert Attermann, CEO of Abrams Artists Agency, confirmed the news to variety.com.
No further details were immediately available.
Leibman, a native of New York, played Dr. Leonard Green on "Friends" as a no-nonsense father who gave grief to David Schwimmer's character Ross, the romantic interest of Aniston's Rachel.
He received an Emmy Award in 1979 for portraying a reformed convict who became a criminal attorney in the series "Kaz".
Leibman won a Tony Award in 1993 for playing a fictional version of Roy Cohn in Tony Kushner's "Angels in America: Millennium Approaches".
Leibman broke into the entertainment business in 1956 on the soap opera "The Edge of Night" and made his movie debut in the 1970 comedy "Where's Poppa?", portraying the brother of George Segal's character.
He starred with Segal in 1972's "The Hot Rock", portrayed a prisoner of war in George Roy Hill's "Slaughterhouse-Five" and a renegade NYPD officer in Gordon Parks' "The Super Cops".
Leibman starred opposite Sally Field as a dedicated union rep in 1979's "Norma Rae", for which Field won her first Oscar. Other credits included "Your Three Minutes Are Up", "Rhinestone", "Night Falls on Manhattan", "Auto Focus" and "Garden State".
He made his Broadway debut in 1963 in "Dear Me, The Sky Is Falling" and was honoured with Drama Desk Awards in 1969 and 1970 for his performances in "We Bombed in New Haven" and "Transfers".
Survivors include his wife, actress Jessica Walter, whom he married in 1983, and his stepdaughter Brooke Bowman, a TV programming executive. He was married from 1969 to 1981 to actress Linda Lavin.
( With inputs from IANS )