Discovered by Alex Gordon (I) as an unproduced screenplay by Hollywood writer Frank Quattrocchi, the film as assigned to be the directorial debut of writer Ian Curteis. However, due to his lack of experience, he ran into several problems during shooting. As the film fell behind schedule and the budget kept increasing, Curteis was fired during the film's final stages. Producer John Croydon replaced him; however, Croydon remained uncredited as the producers did not wish to publicize the problems that had occurred on set.
Actor Bryant Halliday was the cofounder of Janus Films and The Criterion Collection, dedicated to preserving the world's best and most influential films.
Two versions of the morgue scene were shot. In the North American cut, the coroner removes the sheet from the female victim exposing her face only. In the U.K./European cut, the coroner removes the sheet revealing her breasts as well.
Bryant Haliday was cast as Prof. Steiner because producer Alex Gordon (I) was opposed to a British actor playing the title role, and the budget would not allow a Hollywood star to be used. The fact that Gordon was already familiar with him, having cast him in Cuse of the Voodoo (1965) and Devil Doll (1964) was also a factor. Haliday, a fan of horror movies, enjoyed doing the film.
Shot at the same time as Island of Terror (1966), with which it was released on a double bill. The idea of the double bill came to Richard Gordon (III) when he ran Island of Terror (1966) for the Universal Pictures executive in charge, Hi Martin. As the film's special effects were not yet finished, Gordon showed Martin "Island of Terror." Martin enjoyed the film and obtained the American rights for a "very large sum of money." As Gordon was not keen on the idea of "Island of Terror" being placed at the bottom of the bill with one of Universal's other features, which he described as "no good for [our production company] financially," he proposed adding a second film, noting that "The Projected Man" was nearing completion. He showed an unfinished work print of the film to see if Martin was interested, and he enjoyed it enough to accept the deal.