This is the only one of Ray Harryhausen's films to be shot in anamorphic widescreen (2.35:1) due to the difficulty of compositing images in his Dynamation Process. Many of the models had to be sculpted in the "squeezed" dimensions so that when they were photographed with a spherical lens, they would appear in their normal shape in projection.
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.
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.
The original H.G. Wells book has an atmosphere on the moon, so the characters required no space suit of any type, making the diving suits worn by the characters an addition of the filmmakers. However, Wells' speculation of a Lunar atmosphere could have been proved wrong in his own time by the fact that it would be visible as a haze around the limbs of the moon's disk.
Last film of Paul Carpenter.
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.
Composer Bernard Herrmann, who created the music scores for Charles H. Schneer and Ray Harryhausen's previous four films, was originally considered to compose the music score for this film, but he asked for a bigger salary, and because Schneer and Harryhausen's films were low-budget, they, unfortunately, could not meet his price, therefore, Laurie Johnson was chosen instead.
The astronauts in the modern section were dubbed by Robert Rietty, Tim Turner and Ray Barrett.
The Russian spoken by the astronauts at the film's beginning is in fact Czech.
Professor Cavor calls out "SOS" when he becomes stuck between the rocks on the moon's surface. However, SOS did not come into use until 1905, six years later.
It is unknown who did the voices for the moon alien leaders.
Based on the time frames of the story and Edward Judd's age, Arnold Bedford would be 97 years old in the 1964 scenes.
Cavor, around 1h25m, says that the eclipse of the moon is "on the 12th [of May 1899]". Actually, there was no such eclipse in that month, nor even a requisite full moon on or near that date. There was, however, a total eclipse of the moon in the following month, on 23 June 1899.
Dymchurch Town Hall near the beginning is actually Chertsey Town Hall in Surrey.
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.