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)
Fred Holliday
Military Computer Entry - Missile Launch (uncredited)
Robert Quarry
Scientist (uncredited)
Don Ross
Logan US Air Force (uncredited)
William Traylor
Party Guest (uncredited)