In the 1950s and 1960s, he performed on the stage and a few TV roles. Among his many television appearances, he guest-starred in 1964 with Efrem Zimbalist, Jr. in the episode "Super-Star" of the CBS drama series The Reporter. Early in 1967, he appeared in Barry Sullivan's NBC western series The Road West in the episode "Reap the Whirlwind". In 1969, he starred opposite Patty Duke in the film Me, Natalie. Farentino was one of the lawyers in NBC's TV series The Bold Ones (1969–1972), which also starred Burl Ives and Joseph Campanella. He made two appearances in the 1970s anthology television series Night Gallery, once with then-wife Michele Lee ("Since Aunt Ada Came to Stay"), and next with Actress Joanna Pettet ("The Girl w the Hungry Eyes"). In 1973, he appeared in the episode "The Soft, Kind Brush" of the romantic anthology series Love Story. During the 1970s, he appeared on NBC's Cool Million.