Dana Andrews was so impressed with director Jacques Tourneur that when he returned to the United States he had Tourneur direct his next film, The Fearmakers.
Jacques Tourneur originally planned to shoot the movie without directly showing the monster, but the studio pressured him to add it for commercial reasons towards the end of filming.
Beginning in the 1980s, Columbia Pictures replaced their edited 83-minute U.S. version with the uncut original 95-minute version while retaining the U.S. title "Curse of the Demon." The various video releases, and pay-tv showings, have used this restored version. A DVD release contained both versions.
In interviews regarding this film, Dana Andrews credits the story to Oliver Onions. The story is actually based on "Casting the Runes" by M.R. James.
Joanna Harrington's license plate includes the numbers "666", the traditional "Mark of the Beast."
Peggy Cummins's convertible sports car is a Sunbeam Alpine Mark I - manufactured by the Rootes Group in Ryton and Park Royal, London, England from 1953 to 1955, license plate NLJ 666.
Released in the U.S. as the lower half of a double bill with Hammer's The Revenge of Frankenstein.
The source story for this film, "Casting of the Runes", was also adapted into a radio play of that name for the anthology radio program "Escape".
This film was mentioned in the opening song from The Rocky Horror Picture Show ("Science Fiction Double Feature"): "Dana Andrews said prunes gave him the runes, but passing them used lots of skill".
This is the movie that the line "It's in the trees! It's coming!" was sampled from for the opening of Kate Bush song "The Hounds of Love".