Gregory Peck
Robert Thorn

Lee Remick
Katherine Thorn

David Warner
Keith Jennings

Billie Whitelaw
Mrs. Baylock

Harvey Stephens
Damien Thorn

Patrick Troughton
Father Brennan

Martin Benson
Father Spiletto

Robert Rietti
Monk

Tommy Duggan
Priest

John Stride
Psychiatrist

Holly Palance
Young Nanny

Anthony Nicholls
Dr. Becker

Roy Boyd
Reporter

Sheila Raynor
Mrs. Horton

Robert MacLeod
Horton

Bruce Boa
Thorn's Aide

Don Fellows
Thorn's Second Aide

Miki Iveria
First Nun

Betty McDowall
American Secretary

Nicholas Campbell
Marine

Burnell Tucker
Secret Service Man (uncredited)

Ronald Leigh-Hunt
Gentleman at Rugby Match (uncredited)

Guglielmo Spoletini
Italian Taxi Driver (uncredited)

Michael Byrne
Monk (uncredited)

Leo McKern
Carl Bugenhagen (uncredited)

Michael Leader
Rugby Match Spectator (uncredited)