This is the only one of Ray Harryhausen's films to be shot in anamorphic widescreen (2.35:1) due to the higher cost of anamorphic camera and projection lenses needed for his Dynamation Process.
In the book, the large monster which the Selenites hunt is called a Mooncalf. This is an old English term for idiot, since it was believed that being out under a full moon could cause madness (think also "lunatic"), but is also a clever pun on H.G. Wells' part, as the Selenites also hunt this beast like cattle, the young of which is called a calf.
William Rushton was originally supposed to play the bailiff's man in the film, but he was taken ill on the morning he was due to do his one brief scene. Peter Finch, who was working on an adjoining soundstage on The Pumpkin Eater (1964), replaced him at the last minute.
Selenites were played by cockney street kids.
The character of Katherine Callender does not appear in the original H.G. Wells book. Her being from Boston is possibly an allusion to the Jules Verne Moon stories, where the lunar exploration society was based in that city.
Peter Finch: appears briefly in the uncredited role of the bailiff's man, around 0:43:43. He was reputedly only visiting the set when the original actor assigned to play the part failed to show up.