 | Gene Evans als Steve Karnes |
 | André Morell als Prof. James Bickford |
 | Leigh Madison als Jean Trevethan |
 | John Turner als John |
 | Alastair Hunter als Dr. C. A. Morris, the village doctor |
 | Lloyd Lamble als Senior Admiral, at the Admiralty |
 | Jack MacGowran als Dr. Sampson, the paleontologist |
 | Maurice Kaufmann als Mini Submarine Officer |
 | Henri Vidon als Tom Trevethan |
 | Patrick Jordan als Photo Lab Aide |
 | Howard Lang als Naval Commader, at the "Valkyrie" wreck (uncredited) |
 | Leonard Sachs als Dialogue Scientist at Conference (bit) |
| Ernest Blyth als Scientist at Conference (uncredited) |
| Neal Arden als TV Newscaster (uncredited) |
| Paul Beradi als Man Listening to Car Radio (uncredited) |
 | Max Faulkner als PLA Radio Operator (uncredited) |
 | Neil Hallett als Dr. Sampson's Helicopter Pilot (uncredited) |
 | André Maranne als French Radio Officer (uncredited) |
 | Derren Nesbitt als The Radar Operator, at the radar room (uncredited) |
 | Guy Standeven als Naval Officer in Situation Room (uncredited) |
| Eugène Lourié | Screenplay |
| Robert Abel | Story |
| Eugène Lourié | Director |
| Douglas Hickox | Director |
| Daniel James | Screenplay |
| Alan J. Adler | Story |
| Ken Hodges | Director of Photography |
| Lee Doig | Editor |
| David Diamond | Producer |
| Harry White | Art Direction |
| Ted Lloyd | Producer |
| Edwin Astley | Original Music Composer |
| Eugène Lourié | Production Design |
| Willis H. O'Brien | Special Effects |
| Louis DeWitt | Special Effects |
| Desmond Davis | Camera Operator |
| Bernadette Ibbetson | Hairstylist |
| Pete Peterson | Special Effects |
| Jack Rabin | Special Effects |
| Jimmy Evans | Makeup Artist |
| Irving Block | Special Effects |
| Richard Marden | Sound Editor |
| Kim Mills | First Assistant Director |
| Edwin Astley | Conductor |
| Jacques de Lane Lea | Production Manager |
| Sid Wiles | Sound |
| Freda Gibson | Wardrobe Master |
| Jennifer Herrinshaw | Continuity |
| Willis H. O'Brien | Visual Effects |
