Audrey Hepburn was originally offered the role of Joan. Rumor had it she turned it down because her husband, Mel Ferrer, wasn't offered the role of the Dauphin, but Ferrer denied this.
Kenneth Haigh was cast at short notice replacing a actor who pulled out.
Desmond Dickinson started as Director of Photography, but was replaced.
A special effects accident caused actress Jean Seberg actually to catch fire in the scene where Joan of Arc is burned. (She Seberg sustained only very minor injuries.)
Screenwriter Graham Greene, a very famous author himself, added some lines to the original Shaw play when he adapted it for the film, such as Warwick's "She'll burn - before the Pope gets to hear of it!"
The character of Brother Stogumber is given some lines that were originally spoken by the Chaplain in the play.