Roddy McDowall

Cornelius

Kim Hunter

Dr. Zira

Bradford Dillman

Dr. Lewis Dixon

Natalie Trundy

Dr. Stephanie 'Stevie' Branton

Eric Braeden

Dr. Otto Hasslein

William Windom

The President

Sal Mineo

Dr. Milo

Albert Salmi

E-1

Jason Evers

E-2

John Randolph

Committee Chairman

Harry Lauter

General Winthrop

M. Emmet Walsh

Aide

Roy Glenn

Lawyer (as Roy E. Glenn Sr.)

Peter Forster

Cardinal

Norman Burton

Army Officer

William Woodson

Naval Officer

Tom Lowell

Orderly

Gene Whittington

Marine Captain

Donald Elson

Curator

Bill Bonds

TV Newscaster

Army Archerd

Referee

James Bacon

General Faulkner

Ricardo Montalban

Armando

John Alderman

Marine Corporal (uncredited)

Alan Baxter

General (uncredited)

Jack Berle

Secretary of State (uncredited)

Paul Bradley

Official at Briefing (uncredited)

Karl Bruck

German Newscaster (uncredited)

Sam Chew Jr.

Undetermined (uncredited)

Robert Cole

Reporter (uncredited)

Walker Edmiston

Talking Baby Chimp (uncredited) (voice)

Sig Frohlich

Spectator (uncredited)

James W. Gavin

Helicopter Pilot (uncredited)

George Golden

Official at Briefing (uncredited)

James Gonzalez

Official at Briefing (uncredited)

Joe Gray

Bodyguard (uncredited)

Bob Harks

Aide (uncredited)

Linda Harrison

Nova (archive footage) (uncredited)

Elizabeth Harrower

Reporter at Hotel (uncredited)

Shep Houghton

Bystander (uncredited)

Joseph La Cava

Waiter (uncredited)

Robert Nichols

Reporter (uncredited)

Ron Pinkard

Undetermined (uncredited)

Janos Prohaska

Heloise (uncredited)

Tony Regan

Reporter at Hotel (uncredited)

Stephen Roberts

Gen. Brody (uncredited)

Hank Robinson

Reporter (uncredited)

James B. Sikking

Control Room Officer (uncredited)

Jack Slate

Reporter (uncredited)

Arthur Tovey

Official at Briefing (uncredited)

William Tregoe

Hotel Receptionist (uncredited)

William Beckley

British News Anchor (uncredited)