The original plan was to shoot on location in Italy but this proved too expensive so the film was made at Bray Studios outside London, home to the Hammer horror movies. Some location work was done in Romania and Cyprus. Shooting in Romania proved to be rather difficult, given that there was hardly anything of a native film industry and also because the country was very tightly controlled by the Communist regime.
While the story of Pope Joan is now widely considered to be fictitious, there is still a minority movement that believes that there actually was a female Pope. Certainly this film treats the legend as if it was fact.
After a muted critical response, the film was severely re-edited. In its original incarnation, the film contained many flashbacks and flash-forwards, quite a progressive style for 1972. These were all removed to create a more linear story and the film was then released as "The Devil's Imposter". These changes were reinstated for a 2009 reissue.