The Keys of the Kingdom was released as a motion picture in 1944 by Paramount. Directed by John M. Stahl, it starred Gregory Peck, Thomas Mitchell, Vincent Price, Roddy McDowall, and Peggy Ann Garner. Critics had less praise for the film than might have been expected. They were largely disappointed with the trite ways in which the film dealt with difficult issues in the novel.

A film version of The Citadel, starring Robert Donat and produced by MGM, appeared in 1938 and was voted the best film of that year by the New York Film Critics. It appeared more recently, starring Ben Cross, in a ten- part series on Masterpiece Theatre on public television.