William O'Malley

Father Joseph Kevin Dyer

Kitty Winn

Sharon Spencer

Jack MacGowran

Burke Dennings

Barton Heyman

Dr. Klein

Peter Masterson

Dr. Barringer

Rudolf Schündler

Karl

Gina Petrushka

Willi

Robert Symonds

Dr. Taney

Arthur Storch

Psychiatrist

Thomas Bermingham

Tom

Vasiliki Maliaros

Mary Karras

Titos Vandis

Uncle John

John Mahon

Language Lab Director

Wallace Rooney

Bishop Michael

Ron Faber

Chuck / Demon (voice)

Donna Mitchell

Mary Jo Perrin

Roy Cooper

Jesuit Dean

Robert Gerringer

Senator at Party

Mercedes McCambridge

Demon (voice)

Paul Bateson

Radiologist's Assistant (uncredited)

Elinore Blair

Nurse (uncredited)

William Peter Blatty

The Producer (uncredited)

Mary Boylan

First Mental Patient (uncredited)

Dick Callinan

Astronaut (uncredited)

Mason Curry

Doctor (voice) (uncredited)

Toni Darnay

Violent psychotic patient (uncredited)

Eileen Dietz

Demon / Regan Double (uncredited)

Joanne Dusseau

Senator's Wife (uncredited)

Bernard Eismann

Minor Role (uncredited)

Beatrice Hunter

Minor Role (uncredited)

Yvonne Jones

Bellevue Nurse (uncredited)

Don LaBonte

Minor Role (uncredited)

Barton Lane

Angiography Doctor (uncredited)

Ann Miles

Spiderwalk (uncredited)

John Nicola

Priest (uncredited)

Vincent Russell

Subway Vagrant (uncredited)

Gerard F. Yates

Priest Singing Around Piano at Party (uncredited)

Rita Sakellariou

(her voice on the radio)