Eric Braeden
Dr Charles Forbin

Susan Clark
Dr. Cleo Markham

Gordon Pinsent
The President

William Schallert
CIA Director Grauber

Georg Stanford Brown
Dr. John F. Fisher

Willard Sage
Dr. Blake

Alex Rodine
Dr. Kuprin

Martin E. Brooks
Dr. Jefferson J. Johnson

Marion Ross
Angela Fields

Dolph Sweet
Missile Commander

Byron Morrow
Secretary of State

Lew Brown
Peterson

Sid McCoy
Secretary of Defense

James Hong
Dr. Chin

Robert Cornthwaite
First Scientist

Tom Basham
Thomas L. Harrison

Leonid Rostoff
Russian Chairman

Serge Tschernisch
Translator

John Davey
Military officer on phone (uncredited)

Paul Frees
Colossus (voice) (uncredited)