 Gregory PeckRobert Thorn | Robert Thorn |
 Lee RemickKatherine Thorn | Katherine Thorn |
 David WarnerKeith Jennings | Keith Jennings |
 Billie WhitelawMrs. Baylock | Mrs. Baylock |
 Harvey StephensDamien Thorn | Damien Thorn |
 Patrick TroughtonFather Brennan | Father Brennan |
 Martin BensonFather Spiletto | Father Spiletto |
 Robert RiettiMonk | Monk |
 Tommy DugganPriest | Priest |
 John StridePsychiatrist | Psychiatrist |
 Holly PalanceYoung Nanny | Young Nanny |
 Anthony NichollsDr. Becker | Dr. Becker |
 Roy BoydReporter | Reporter |
 Sheila RaynorMrs. Horton | Mrs. Horton |
 Robert MacLeodHorton | Horton |
 Bruce BoaThorn's Aide | Thorn's Aide |
 Don FellowsThorn's Second Aide | Thorn's Second Aide |
| PPatrick McAlinneyPhotographer | Photographer |
| DDawn PerllmanChambermaid | Chambermaid |
| NNancy MannighamNurse | Nurse |
 Miki IveriaFirst Nun | First Nun |
 Betty McDowallAmerican Secretary | American Secretary |
 Nicholas CampbellMarine | Marine |
 Burnell TuckerSecret Service Man (uncredited) | Secret Service Man (uncredited) |
 Ronald Leigh-HuntGentleman at Rugby Match (uncredited) | Gentleman at Rugby Match (uncredited) |
 Guglielmo SpoletiniItalian Taxi Driver (uncredited) | Italian Taxi Driver (uncredited) |
 Freda DowieNun (uncredited) | Nun (uncredited) |
 Ya'ackov BanaiArab (uncredited) | Arab (uncredited) |
| HHarvey BernhardMan Walking across Street (uncredited) | Man Walking across Street (uncredited) |
 Michael ByrneMonk (uncredited) | Monk (uncredited) |
