 | Don Knotts als Henry Limpet |
 | Carole Cook als Bessie Limpet |
 | Jack Weston als George Stickel |
 | Andrew Duggan als Harlock |
 | Larry Keating als Admiral P.P. Spewter |
 | Oscar Beregi Jr. als Nazi Admiral (as Oscar Beregi) |
 | Charles Meredith als Fleet Admiral |
 | Elizabeth MacRae als Ladyfish (voice) |
 | Paul Frees als Crusty (voice) |
 | Wesley Gale als Man Staring Into Window (uncredited) |
 | Peter Adams als Lieutenant (uncredited) |
| Leon Alton als Officer at Fleet Admiral's Meeting (uncredited) |
 | Phil Arnold als Short Fisherman (uncredited) |
| George Bruggeman als Nazi Officer (uncredited) |
| Paul Busch als Sonar Man (uncredited) |
 | Al Checco als Sailor (uncredited) |
| Cordy Clark als Giggling Girl (uncredited) |
 | Roydon Clark als Sailor (uncredited) |
 | Sayre Dearing als Passerby/Naval Officer at Meeting (uncredited) |
| George DeNormand als Nazi Officer (uncredited) |
| Dan Dowling als Naval Officer at Meeting (uncredited) |
| Harold Dyrenforth als U-Boat Captain (uncredited) |
 | Louie Elias als Sailor (uncredited) |
| Lisabeth Field als Miss Barnes (uncredited) |
| Logan Field als Lieutenant (uncredited) |
| Fred Fisher als Officer at Fleet Admiral's Meeting (uncredited) |
| Walter Friedel als Nazi Officer (uncredited) |
| George Golden als Naval Officer at Fleet Admiral Meeting (uncredited) |
| Marv Goux als Nazi Officer (uncredited) |
| John Hale als Sailor (uncredited) |
| Sam Harris als Officer at Fleet Admiral's Briefing (uncredited) |
 | George Holmes als Scientist (uncredited) |
| Joseph La Cava als Officer at Fleet Admiral's Briefing (uncredited) |
| Mike Lally als Naval Officer at Meeting (uncredited) |
 | Harold Miller als Officer at Fleet Admiral's Briefing (uncredited) |
 | Charles Morton als Boat Captain (uncredited) |
| Henry Norell als Sailor (uncredited) |
| Jack Pepper als Sport Fishmern (uncredited) |
| Montie Plyler als Helmsman (uncredited) |
| Felix Reinsch als Submarine Captain (uncredited) |
| Waclaw Rekwart als Passerby (uncredited) |
| Heinz Sadler als Sonar Man (uncredited) |
 | Scott Seaton als Old Man in Shipping Office (uncredited) |
| Jack Shea als Sailor (uncredited) |
| John Truax als Policeman (uncredited) |
| Edward Wermel als Scientist (uncredited) |
 | Feridun Çölgeçen als Scientist (uncredited) |
| Arthur Lubin | Director |
| Jameson Brewer | Screenplay |
| John C. Rose | Screenplay |
| Joe DiMona | Adaptation |
| Theodore Pratt | Novel |
| John W. Dunn | Story Supervisor |
| Gerry Chiniquy | Animation Director |
| Robert McKimson | Animation Director |
| Hawley Pratt | Animation Director |
| Bill Tytla | Animation Director |
| John C. Rose | Producer |
| Frank Perkins | Music |
| Harold E. Stine | Director of Photography |
| Donald Tait | Editor |
| LeRoy Deane | Art Direction |
| William L. Kuehl | Set Decoration |
| Gordon Bau | Makeup Supervisor |
| Jean Burt Reilly | Hairstylist |
| Bill Phillips | Makeup Artist |
| Louis Phillips | Makeup Artist |
| Lenore Weaver | Hairstylist |
| Sergei Petschnikoff | Assistant Director |
| Edmond F. Bernoudy | Assistant Director |
| Ira Stewart | Assistant Director |
| Stanley Jones | Sound |
| Paul Burnett | Gaffer |
