Kubrick was told that in order to get funding from Warner's, he had to cast one of the "top 10" current actors. Ryan O'Neal, coming off the success of Love Story, was #2. Redford was #4. Kubrick wisely chose Redford, but Redford turned down the role in preference for George Roy Hill's unremarkable the Great Waldo Pepper. Ryan O'Neal did get the role of Barry Lyndon. Kubrick was reportedly pacing the set his first day on camera, saying, "OMG, he really can't act!"

Oskar Werner (from Jules and Jim fame) was cast as Prussian Captain Potzdorf. He was fired after three weeks of shooting.