 | Gene Barry als Dr. Clayton Forrester |
 | Ann Robinson als Sylvia Van Buren |
 | Lewis Martin als Pastor Dr. Matthew Collins |
 | Les Tremayne als Maj. Gen. Mann |
 | Frank Kreig als Fiddler Hawkins (uncredited) |
 | Vernon Rich als Col. Ralph Heffner |
 | Sandro Giglio als Dr. Bilderbeck |
 | Ann Codee als Dr. Duprey (uncredited) |
 | Robert Cornthwaite als Dr. Pryor (as Bob Cornthwaite) |
 | Cedric Hardwicke als Commentary (voice) (as Sir Cedric Hardwicke) |
 | Houseley Stevenson Jr. als Gen. Mann's Aide (as Housely Stevenson Jr.) |
 | William Phipps als Wash Perry (as Bill Phipps) |
 | Jack Kruschen als Salvatore |
 | Paul Birch als Alonzo Hogue (uncredited) |
 | Paul Frees als Second Radio Reporter / Opening Announcer |
 | Henry Brandon als Cop at Crash Site |
| Peter Adams als Pine Summit Fire Watcher (uncredited) |
 | Eric Alden als Man (uncredited) |
| Hugh Allen als Brigadier General (uncredited) |
| Ruth Barnell als Mother (uncredited) |
 | Edgar Barrier als Prof. McPherson (uncredited) |
 | Russ Bender als Dr. Carmichael (uncredited) |
| Oscar Blank als Man in Church (uncredited) |
| Nick Borgani als Man in Church (uncredited) |
| Hazel Boyne als Screaming Woman (uncredited) |
 | Chet Brandenburg als Man in Church (uncredited) |
| George Bruggeman als Soldier (uncredited) |
| Nora Bush als Woman in Church (uncredited) |
| Tony Butala als Boy in Final Church (uncredited) |
| Mushy Callahan als Burning Soldier at Pit (uncredited) |
| Dick Cherney als Looter (uncredited) |
 | Edward Colmans als Spanish Priest (uncredited) |
| James Conaty als Man at Pacific Institute of Science and Technology (uncredited) |
 | Russ Conway als Rev. Bethany (uncredited) |
| Martin Coulter als Marine Sergeant (uncredited) |
| Vittorio Cramer als First Radio Reporter (uncredited) |
 | Pierre Cressoy als Frenchman (uncredited) |
| Oliver Cross als Scientist (uncredited) |
| Jane Crowley als Woman in Church (uncredited) |
| Jim Davies als Marine Commanding Officer (uncredited) |
| Helen Dickson als Woman in Church (uncredited) |
 | Ralph Dumke als Buck Monahan (uncredited) |
| Jimmie Dundee als Civil Defense Official (uncredited) |
 | Al Ferguson als Police Chief (uncredited) |
| Dick Fortune als Marine Captain (uncredited) |
| Alex Frazer als Dr. James (uncredited) |
| Frank Freeman Jr. als Bum #2 Listening to Radio (uncredited) |
| Slim Gaut als Radio Listener (uncredited) |
 | Charles Gemora als Martian (uncredited) |
 | Ned Glass als Well-Dressed Looter (uncredited) |
| Jack Gordon als Man in Church (uncredited) |
 | Fred Graham als Looter (uncredited) |
| Joe Gray als Looter (uncredited) |
 | Herman Hack als Worker Listening to Radio (uncredited) |
 | Nancy Hale als Young Wife (uncredited) |
| Virginia Hall als Girl (uncredited) |
 | Ted Hecht als KGEB Reporter (uncredited) |
 | Douglas Henderson als Staff Sergeant (uncredited) |
 | Gertrude Hoffmann als Elderly News Vendor (uncredited) |
| Tex Holden als Man in Church (uncredited) |
| Jimmie Horan als Party Guest (uncredited) |
| Patricia Iannone als Girl (uncredited) |
| Jerry James als Reporter (uncredited) |
| Michael Jeffers als Worker Listening to Radio (uncredited) |
 | Dick Johnstone als Man in Church (uncredited) |
 | Carolyn Jones als Blonde Party Guest (uncredited) |
| Don Kohler als Colonel (uncredited) |
 | Ivan Lebedeff als Dr. Gratzman (uncredited) |
 | Freeman Lusk als Secretary of Defense (uncredited) |
 | Herbert Lytton als Chief of Staff (uncredited) |
 | Wilbur Mack als Official (uncredited) |
 | George Magrill als Traffic Cop (uncredited) |
| Mike Mahoney als Townsman (uncredited) |
| John Mansfield als Man (uncredited) |
 | Joel Marston als Military Policeman in Jeep (uncredited) |
| Sydney Mason als Fire Chief, Crew #3 (uncredited) |
 | John Maxwell als Doctor (uncredited) |
| Mathew McCue als Man in Church (uncredited) |
 | David McMahon als Minister, First Church (uncredited) |
| William Meader als P.E. Official (uncredited) |
 | Lee Miller als Reporter (uncredited) |
| Ralph Montgomery als Los Angeles Red Cross Official (uncredited) |
 | Alvy Moore als Zippy (uncredited) |
 | Bob Morgan als Injured Civil Defense Worker (uncredited) |
 | Charles Morton als Worker Listening to Radio (uncredited) |
| George Nardelli als Military Officer (uncredited) |
| Stanley Orr als Marine Major (uncredited) |
 | George Pal als Bum #1 Listening to Radio (uncredited) |
| Walter Richards als Reporter (uncredited) |
 | Robert Rockwell als Forest Ranger at Crash Site (uncredited) |
 | Walter Sande als Sheriff Bogany (uncredited) |
 | James Seay als Air Force Bomber Pilot (uncredited) |
| Allen D. Sewall als Man in Church (uncredited) |
| Lucile Sewall als Woman in Church (uncredited) |
| Cora Shannon als Old Woman (uncredited) |
 | David Sharpe als Looter (uncredited) |
 | Teru Shimada als Japanese Diplomat (uncredited) |
| Reginald Lal Singh als Military Officer (uncredited) |
| Bobby Somers als Deputy at Crash Site (uncredited) |
 | Bert Stevens als Man in Church (uncredited) |
| Charles Stewart als Marine Captain (uncredited) |
 | Jack Stoney als Looter (uncredited) |
| Gus Taillon als Elderly Man (uncredited) |
| Morton C. Thompson als Reporter (uncredited) |
 | Arthur Tovey als Party Guest (uncredited) |
 | Dale Van Sickel als Looter (uncredited) |
 | Dorothy Vernon als Elderly Woman at Square Dance (uncredited) |
| Edward Wahrman als Cameraman (uncredited) |
 | Anthony Warde als Military Police Driver (uncredited) |
| Bob Whitney als Military Officer (uncredited) |
| Chalky Williams als Worker Listening to Radio (uncredited) |
| Waldon Williams als Boy (uncredited) |
| Bud Wolfe als Rescuing Civil Defense Worker (uncredited) |
| Fred Zendar als Marine Lieutenant (uncredited) |
| Robert S. Richardson | Technical Advisor |
| Gae Griffith | Producer's Assistant |
| Chesley Bonestell | Technical Advisor |
| Monroe W. Burbank | Color Grading |
| George Parrish | Orchestrator |
| Diana Gemora | Costumer |
| Charles Gemora | Costumer |
| Murray Young | Key Grip |
| Soldier Graham | Gaffer |
| Fred Zendar | Stunts |
| Bud Wolfe | Stunts |
| Chalky Williams | Stunts |
| Dale Van Sickel | Stunts |
| Jack Stoney | Stunts |
| Bobby Somers | Stunts |
| David Sharpe | Stunts |
| Charles Morton | Stunts |
| Bob Morgan | Stunts |
| George Magrill | Stunts |
| Tex Holden | Stunts |
| Herman Hack | Stunts |
| Joe Gray | Stunts |
| Fred Graham | Stunts |
| Slim Gaut | Stunts |
| Jimmie Dundee | Stunts |
| Mushy Callahan | Stunts |
| George Bruggeman | Stunts |
| Chet Brandenburg | Stunts |
| Cliff Shirpser | Visual Effects Camera |
| Walter Hoffman | Visual Effects |
| Marcel Delgado | Modeling |
| Jack Caldwell | Visual Effects |
| Irmin Roberts | Visual Effects |
| Paul K. Lerpae | Visual Effects |
| W. Wallace Kelley | Visual Effects |
| Gordon Jennings | Visual Effects |
| Jan Domela | Visual Effects |
| Ivyl Burks | Visual Effects |
| Barney Wolff | Special Effects |
| Aubrey Law | Visual Effects |
| A. Edward Sutherland | Special Effects |
| Ken Strickfaden | Special Effects |
| Bob Springfield | Special Effects |
| Chester Pate | Special Effects |
| Loren L. Ryder | Sound Director |
| Walter Oberst | Sound Effects |
| Lovell Norman | Sound Editor |
| Tommy Middleton | Sound Effects |
| Dan Johnson | Sound Effects |
| Howard Beals | Sound Effects |
| William M. Andrews | Sound Editor |
| Harry Lindgren | Sound Recordist |
| Gene Garvin | Sound Recordist |
| Lee Vasque | Props |
| Milt Olson | Props |
| Gene Lauritzen | Construction Coordinator |
| Charles Davies | Props |
| Gordon Cole | Property Master |
| Ivyl Burks | Props |
| Romaine Birkmeyer | Props |
| Chesley Bonestell | Painter |
| Michael D. Moore | Assistant Director |
| Frank Caffey | Production Manager |
| Wally Westmore | Makeup Supervisor |
| Emile Kuri | Set Decoration |
| Albert Nozaki | Set Decoration |
| Hal Pereira | Art Direction |
| Albert Nozaki | Art Direction |
| Everett Douglas | Editor |
| George Barnes | Director of Photography |
| Leith Stevens | Original Music Composer |
| Cecil B. DeMille | Executive Producer |
| George Pal | Producer |
| Frank Freeman Jr. | Associate Producer |
| Barré Lyndon | Screenplay |
| H.G. Wells | Novel |
| Byron Haskin | Director |
| Edith Head | Costume Design |
