 Eric BraedenDr Charles Forbin | Dr Charles Forbin |
 Susan ClarkDr. Cleo Markham | Dr. Cleo Markham |
 Gordon PinsentThe President | The President |
 William SchallertCIA Director Grauber | CIA Director Grauber |
 Georg Stanford BrownDr. John F. Fisher | Dr. John F. Fisher |
 Willard SageDr. Blake | Dr. Blake |
 Alex RodineDr. Kuprin | Dr. Kuprin |
 Martin E. BrooksDr. Jefferson J. Johnson | Dr. Jefferson J. Johnson |
 Marion RossAngela Fields | Angela Fields |
 Dolph SweetMissile Commander | Missile Commander |
 Byron MorrowSecretary of State | Secretary of State |
| LLew BrownPeterson | Peterson |
 Sid McCoySecretary of Defense | Secretary of Defense |
 James HongDr. Chin | Dr. Chin |
 Robert CornthwaiteFirst Scientist | First Scientist |
 Tom BashamThomas L. Harrison | Thomas L. Harrison |
| LLeonid RostoffRussian Chairman | Russian Chairman |
| SSerge TschernischTranslator | Translator |
| JJohn DaveyMilitary officer on phone (uncredited) | Military officer on phone (uncredited) |
 Paul FreesColossus (voice) (uncredited) | Colossus (voice) (uncredited) |
| FFred HollidayMilitary Computer Entry - Missile Launch (uncredited) | Military Computer Entry - Missile Launch (uncredited) |
 Robert QuarryScientist (uncredited) | Scientist (uncredited) |
 Don RossLogan US Air Force (uncredited) | Logan US Air Force (uncredited) |
 William TraylorParty Guest (uncredited) | Party Guest (uncredited) |
