This was producer Edward Small's attempt to cash in on the huge success of The 7th Voyage of Sinbad (1958). He even hired the same director (Nathan Juran), hero (Kerwin Mathews) and villain (Torin Thatcher).
When Charles Schneer and Ray Harryhausen were looking for a producer for The Seventh Voyage of Sinbad, one of the hopefuls was Edward Small, who turned them down. When Sinbad proved to be a huge hit, Small was determined to duplicate the former movie with the same director and stars. Although he couldn't get Harryhausen, Jim Danforth came close to duplicating Sinbad's monsters with Cormoran, the flying dragon, and the Imp instead of the Cyclops, Dragon, and Genie.
The film was unreleased in the UK until 1967 and then received cuts for an 'A' certificate to edit the witch attack on the ship, Princess Elaine being attacked by the giant, and Jack's fight with the dragon.
Torin Thatcher had been appearing on Broadway in "The Miracle Worker" but quit that role in order to appear in this film.
The film slides neatly into that early 60s sword 'n' fantasy cycle that "Sinbad", "Jason", and "Gulliver" had established. It cashed in by hiring Matthews, Thatcher, and director Juran. Unfortunately the budget didn't allow for Schneer to produce, nor Herrmann to compose, nor Harryhausen to animate, and instead of the exotic coastlines of Spain, had to settle for the Catalina Islands outside Los Angeles.