| Gene Barry | Dr. Clayton Forrester |
| Ann Robinson | Sylvia Van Buren |
| Les Tremayne | Maj. Gen. Mann |
| Robert Cornthwaite | Dr. Pryor |
| Sandro Giglio | Dr. Bilderbeck |
| Lewis Martin | Pastor Dr. Matthew Collins |
| Houseley Stevenson Jr | .Gen. Mann's aide |
| Paul Frees | Radio Reporter |
| William Phipps | Wash Perry |
| Vernon Rich | Col. Ralph Heffner |
| Henry Brandon | Cop at Crash Site |
| Jack Kruschen | Salvatore |
| Cedric Hardwicke | Commentary |
| Vittorio Cramer | Narrator |
| Peter Adams | Pine Summit Fire Watcher |
| Eric Alden | Man |
| Hugh Allen | Brigadier General |
| Ruth Barnell | Mother |
| Edgar Barrier | Prof. McPherson |
| Russ Bender | Dr. Carmichael |
| Paul Birch | Alonzo Hogue |
| Hazel Boyne | Screaming Woman |
| Tony Butala | One of 3 boys in final church scene |
| Mushy Callahan | Burning Soldier at Pit |
| George Cisar | Deputy |
| Ann Codee | Dr. Duprey |
| Edward Colmans | Spanish Priest |
| Russ Conway | Rev. Bethany |
| Martin Coulter | Marine Sergeant |
| Pierre Cressoy | Man |
| Jim Davies | Marine Commanding Officer |
| Ralph Dumke | Buck Monahan |
| Jimmie Dundee | Civil Defense Official |
| Al Ferguson | Police Chief |
| Dick Fortune | Marine Captain |
| Alex Frazer | Dr. James |
| Frank Freeman Jr | .Bum #2 listening to radio |
| Charles Gemora | Martian |
| Ned Glass | Well-Dressed Looter |
| Fred Graham | Looter |
| Joe Gray | Looter |
| Nancy Hale | Young Wife |
| Virginia Hall | Girl |
| Ted Hecht | KGEB Reporter |
| Douglas Henderson | Staff Sergeant |
| Gertrude Hoffman | Elderly Woman News Vendor |
| Patricia Iannone | Girl |
| Jerry James | Reporter |
| Carolyn Jones | Blonde |
| Don Kohler | Colonel |
| Frank Kreig | Fiddler Hawkins |
| Ivan Lebedeff | Dr. Gratzman |
| Rudy Lee | Boy |
| Freeman Lusk | Secretary of Defense |
| Herbert Lytton | Chief of Staff |
| Mike Mahoney | Young Man |
| John Mansfield | Man |
| Joel Marston | MP in Jeep |
| Sydney Mason | Fire Chief, Crew #3 |
| John Maxwell | Doctor |
| David McMahon | Minister, First Church |
| Bill Meader | P.E. Official |
| Ralph Montgomery | Los Angeles Red Cross official |
| Alvy Moore | Zippy |
| Bob Morgan | Injured Civil Defense Worker |
| Stanley Orr | Marine Major |
| George Pal | Bum #1 listening to radio |
| Walter Richards | Reporter |
| Robert Rockwell | Forest Ranger at Crash Site |
| Walter Sande | Sheriff Bogany |
| James Seay | Bomber Pilot |
| Cora Shannon | Old Woman |
| David Sharpe | Looter |
| Teru Shimada | Japanese Diplomat |
| Charles Stewart | Marine Captain |
| Gus Taillon | Elderly Man |
| Morton C. Thompson | Reporter |
| Dale Van Sickel | Looter |
| Dorothy Vernon | Elderly Woman |
| Edward Wahrman | Cameraman |
| Anthony Warde | MP Officer |
| Waldon Williams | Boy |
| Bud Wolfe | Rescuing Civil Defense Worker |
| Fred Zendar | Marine Lieutenant |
