Robert Wagner writes in his memoirs that he was miscast in this film.
Primo Carnera, who played Sligon, had such a thick Italian accent that his voice was dubbed.
Alnwick Castle in Northumberland served as Camelot in all of the master shots while Warwick Castle was used for the main gate and courtyard. Although Alnwick is brown sandstone and Warwick is pale grey stone, carefully placed cameras and lighting masked the difference in shadows.
None of the locations were "stock footage" since this was one of the first CinemaScope movies. The locations were shot by a second unit in Britain during the spring and summer of 1953 specifically for this film. Stand-ins doubled for the principal cast in long shots which were then matched at 20th Century-Fox studios and ranch in California during the autumn of 1953. The English stand-in for Janet Leigh's Aleta character was a teenage Shirley Eaton (later to become the James Bond Goldfinger girl).
Since Prince Valiant's storyline in the comics was so sprawling and complex, the property is said to have languished at MGM where no one could get a handle on it. When MGM eventually passed, Fox picked it up. There, Oscar-winning screenwriter, Dudley Nichols, devised a script by selecting panels from the comic strip to create a much more concise storyboard from which to work.
The average shot length of this film is about 7 seconds. This is fast for an early CinemaScope film, and is low given the 8 - 11 second average of most Hollywood films made between 1930 and 1960.