The actor's son, Efrem Zimbalist III, said his father had been outside water his lawn at his Solvang, Calif., ranch when a handyman found him lying dead in the grass.
“He was healthy, playing golf three days a week, and always in his garden,” the younger Zimbalist said.
The cause of his death wasn't reported.
Zimbalist did most of his work on the small screen, a fact he partly attributed to his unusual last name.
“It’s kept me out of westerns. I can’t imagine a Hopalong Zimbalist," he said during a 1959 interview with the New York Times.
He served in the U.S Army during World War II and was injured in the battle of Hurtgen Forest in 1941.
Zimbalist is survived by his son, daughter Stephanie, four grandchildren and three great-grandchildren.