Mr. Mulligan died at his home Tuesday after a long battle with cancer, publicist Julian Myers said in a prepared statement.
A native of New York, Mr. Mulligan began his nearly 40-year career in show business as an aspiring writer. He fell into acting when he was drafted into playing a role at a rehearsal while trying to sell a play.
From 1977 to 1981, Mr. Mulligan played lovable working-class screwball Burt Campbell â€“ step-father to Billy Crystal's character â€“ on the quirky series Soap. He won an Emmy for the role in 1980.
On Empty Nest, a spinoff of The Golden Girls that ran from 1988 to 1995, Mr. Mulligan played Dr. Harry Weston, a widower with three grown daughters. The part won him another Emmy, in 1989.
"He's certainly different from my role on Soap," Mr. Mulligan said in a 1988 Associated Press interview. "This guy's a good doctor who cares deeply about his patients. He's a good fellow trying to take care of his daughters. His wife died 18 months ago and he still can't take the ring off."
Among the other highlights of Mr. Mulligan's career were performing onstage with James Stewart in Harvey and working with director Blake Edwards in the 1981 film S.O.B., which also starred Julie Andrews and William Holden.
Mr. Mulligan was also featured in 1969's The Undefeated with John Wayne and Rock Hudson, and he portrayed Lt. Col. George Armstrong Custer in the 1970 film Little Big Man.
Mr. Mulligan is survived by his son, James, and brothers Robert, director of films such as To Kill a Mockingbird, and James.