Don Knotts as Henry Limpet

Carole Cook as Bessie Limpet

Jack Weston as George Stickel

Andrew Duggan as Harlock

Larry Keating as Admiral P.P. Spewter

Oscar Beregi Jr. as Nazi Admiral (as Oscar Beregi)

Charles Meredith as Fleet Admiral

Elizabeth MacRae as Ladyfish (voice)

Paul Frees as Crusty (voice)

Wesley Gale as Man Staring Into Window (uncredited)

Peter Adams as Lieutenant (uncredited)

Leon Alton as Officer at Fleet Admiral's Meeting (uncredited)

Phil Arnold as Short Fisherman (uncredited)

George Bruggeman as Nazi Officer (uncredited)

Paul Busch as Sonar Man (uncredited)

Al Checco as Sailor (uncredited)

Cordy Clark as Giggling Girl (uncredited)

Roydon Clark as Sailor (uncredited)

Sayre Dearing as Passerby/Naval Officer at Meeting (uncredited)

George DeNormand as Nazi Officer (uncredited)

Dan Dowling as Naval Officer at Meeting (uncredited)

Harold Dyrenforth as U-Boat Captain (uncredited)

Louie Elias as Sailor (uncredited)

Lisabeth Field as Miss Barnes (uncredited)

Logan Field as Lieutenant (uncredited)

Fred Fisher as Officer at Fleet Admiral's Meeting (uncredited)

Walter Friedel as Nazi Officer (uncredited)

George Golden as Naval Officer at Fleet Admiral Meeting (uncredited)

Marv Goux as Nazi Officer (uncredited)

John Hale as Sailor (uncredited)

Sam Harris as Officer at Fleet Admiral's Briefing (uncredited)

George Holmes as Scientist (uncredited)

Joseph La Cava as Officer at Fleet Admiral's Briefing (uncredited)

Mike Lally as Naval Officer at Meeting (uncredited)

Harold Miller as Officer at Fleet Admiral's Briefing (uncredited)

Charles Morton as Boat Captain (uncredited)

Henry Norell as Sailor (uncredited)

Jack Pepper as Sport Fishmern (uncredited)

Montie Plyler as Helmsman (uncredited)

Felix Reinsch as Submarine Captain (uncredited)

Waclaw Rekwart as Passerby (uncredited)

Heinz Sadler as Sonar Man (uncredited)

Scott Seaton as Old Man in Shipping Office (uncredited)

Jack Shea as Sailor (uncredited)

John Truax as Policeman (uncredited)

Edward Wermel as Scientist (uncredited)

Feridun Çölgeçen as Scientist (uncredited)