Born Cameron Mizell (or Mitzell), he had performed on Broadway before his acting career was interrupted by service as a bombardier in World War Two. He debuted onscreen at war's end in What Next, Corporal Hargrove (1945). Mitchell's reputation was considerably enhanced by his portrayal of Happy in both the stage and screen versions of Death of a Salesman (screen version, 1951); he went on to play intense leads and character roles in numerous films, and starred in the TV series "The Beachcomber," "The High Chaparral," and "Swiss Family Robinson." Later in his career he appeared in many low-budget, low-quality films.