Instead, Dierkes went to work for the U.S. Treasury Department which coincidentally sent him to Hollywood to function as technical advisor for the film To the Ends of the Earth (1948) and Orson Welles cast him as Ross in his version of Macbeth in the same year.

Because of his appearance and very tall frame (6 ft 6 in), Dierkes enjoyed a long career as a character actor, often portraying either villains or soldiers.

One noteworthy performance cast Dierkes as the compassionate and caring scientist Dr. Chapman in the 1951 film The Thing from Another World which remains a mainstay science fiction classic of the 1950s.

Dierkes portrays a Tennessean named Jocko, who is torn between leaving before the attack to care for his blind wife, or staying to support the Texans' cause.

His other film credits included The Naked Jungle (1954), The Raid (1954), Jubal (1956), The Daughter of Dr. Jekyll (1957), Blood Arrow (1958), The Left Handed Gun (1958), The Buccaneer (1958), The Hanging Tree (1959), The Oregon Trail (1959), One-Eyed Jacks (1961), The Premature Burial (1962), X: The Man with the X-ray Eyes (1963), The Haunted Palace (1963), The Omega Man (1971) and Rage (1972).