Released on a double bill with The Terrornauts (1967). Director Freddie Francis claimed that the company had spent all their budget on that film, leaving nothing left for They Came from Beyond Space (1967).
Allegedly this was Anwar Sadat's favorite movie.
To save costs, the production used many sets and props from the Amicus movie Daleks' Invasion Earth 2150 A.D. (1966) filmed earlier.
In the laboratory where they cast the silver cage stands a big clear plastic (or glass) gun. This is the same prop used as the main device in The Projected Man (1966).