Born Jack Weinstein, he began training for the stage at the Cleveland Playhouse at age ten. Weston dropped out of school at 15, working occasionally as a stage actor before serving in World War Two; during the war he often performed with the USO. At war's end he moved to New York and studied at the American Theater Wing, meanwhile working in odd jobs. In 1950 he began getting featured roles on Broadway and TV, then entered movies in 1958; with intermittent breaks, he remained busy in films throughout the next three decades. In the mid '70s he gained new popularity as the star of Neil Simon's play California Suite. He married actress Marge Redmond.