Blossom began appearing on screen in 1958. His first appearance in a feature film was in 1971's "The Hospital" starring George C. Scott. During the 1970s he had roles in films including "The Great Gatsby" (1974) starring Robert Redford and Mia Farrow, "Slaughterhouse-Five" (1972), Steven Spielberg's "Close Encounters of the Third Kind" (1977), and "Escape from Alcatraz" (1979) starring Clint Eastwood. "Escape from Alcatraz" is perhaps Blossom's best known supporting role for the scene where he chopped off his fingers with an axe.