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 during the 1950s. His performance provided sanity and calm amid the tension and chills of the action thriller. Although playing against type, his low tone and measured monotone dialogue was a good counter to the rapid and chaotic overlapping dialogue throughout the movie, giving brief pauses between each actors lines as the tension in each scene increased. In 1951 played a soldier next to Audie Murphy in the classic film, Red Badge of Courage. In the 1953 film Shane, Dierkes portrays the callous Morgan Ryker with great effect, Director George Stevens making good use of Dierkes' craggy features. Alongside his 'brother' Rufus (Emile Meyer) and Jack Wilson (Jack Palance) he makes up a trio of villainous characters who are despatched by the title character, Shane, in the final bar room shootout. One of his more memorable scenes is in the 1960 film, The Alamo. 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. Understanding that if Jocko stays to fight she will likely be widowed, Jocko's wife coaxes him to stay and defend the fort, despite her disability.