- Akira Takarada
- Dr. Ken Tashiro
- Joseph Cotten
- Capt. Craig McKenzie / Cmdr. Glenn McKenzie
- Cesar Romero
- Dr. Malic / Lt. Hastings
- Richard Jaeckel
- Perry Lawton
- Patricia Medina
- Lucretia
- Linda Haynes
- Dr. Anne Barton
- Masumi Okada
- Dr. Jules Masson
- Hikaru Kuroki
- Capt. Kuroiga
- Akihiko Hirata
- Dr. Sugata
- Susumu Kurobe
- Chin
- Wataru Ãmae
- Kobo
- Haruo Nakajima
- Flying Lion / Giant Rat
- Tetsu Nakamura
- Dr. Okada
- Mari Nakayama
- Tsuruko Okada
- Burr Middleton
- Additional Voices
- Shigeo Katô
- Marine observer
- Eisaburo Komatsu
- Reporter
- Akio Kusama
- Marine Vessel scorer
- Kôichi Satô
- Medical Petty Officer of Recovery Ship
- Masaaki Tachibana
- News Reporter
- Enver Altenbay
- Minor Role
- Teruo Aragaki
- Other Giant Rat
- Kathy Horan
- Correspondent of the base
- Andrew Hughes
- Sir Maurice Poeley
- Yoshio Katsube
- Ocean Observation Vessel Recorder / Latitude Zero resident (uncredited)
- Peggy Neal
- Correspondent of the base B.
- Seiji Onaka
- Sailor on escort ship
- Yû Sekita
- Bat Man / Seaman (uncredited)
- Peter Williams
- Shirtless man at resort.
- Osman Yusuf
- Man with Gun
