He initially appeared in only unbilled (e.g., "Flying Leathernecks", RKO 1951) and extra roles before gradually receiving bigger character parts. Mitchum supported his more famous brother on several occasions, and became known as the friendly, food-loving Inspector Frank DiGiorgio in the first three Dirty Harry films. Mitchum was one of only four actors to appear in more than one film in this series (the others being Clint Eastwood, Harry Guardino and Albert Popwell), and with Eastwood and Guardino, he was one of only three actors to play the same character in each appearance. His character was killed in the third film, The Enforcer.