Actor James Mason acted as a sponsor to the production for actor Sam Neill. Mason originally suggested to the film's producers that they should check out Neill. Producer Harvey Bernhard had Neill flown in to London for an audition, paid for by Mason. Neill later reimbursed Mason for the airfare. Neill drew on some of Mason's mannerisms for his performance and characterization.
The film's title when originally theatrically released in 1981 was "The Final Conflict" but the film has since generally become re-titled and now known as "Omen III: The Final Conflict" in order to for the movie to include the word "Omen" which exists as part of the title of all three other films in the series, The Omen (1976), Damien: Omen II (1978) and Omen IV: The Awakening (1991).
At the time of filming, Sam Neill and Lisa Harrow developed an off-camera relationship that produced son Tim Neill.
(at around 1h) Stuntman Vic Armstrong claims, for the 2005 book of 'Guinness World Records', that his backwards 100 foot fall from a bridge was one of the scariest stunts he ever performed. The majority of Armstrong's jumps in the past had been less than 70 foot drops.
(at around 1h 3 mins) The sequence where Damien Thorn speaks to a crowd of his followers was filmed in a Yorkshire quarry with around 450 extras. The scenes were shot with a very low level of available light.
Harvey Bernhard: (at around 11 mins) Uncredited, the film's producer as a US Embassy press secretary.