Raymond Burr as Steve Martin

Akira Takarada as Ogata

Akihiko Hirata as Dr. Serizawa

Takashi Shimura as Dr. Yamane

Momoko Kôchi as Emiko Yamane

Emilio Cigoli as Steve Martin (voice)

Rita Savagnone as Emiko Yamane (voice)

Giuseppe Rinaldi as Ogata (voice)

Vittorio Cramer as George Lawrence (voice) (as Vittorio Kramer)

Pino Locchi as Security Officer Tomo Iwanaga (voice)

Sachio Sakai as Hagiwara (uncredited)

Fuyuki Murakami as Dr. Tabata (uncredited)

Ren Yamamoto as Seiji (uncredited)

Toyoaki Suzuki as Shinkichi (uncredited)

Tadashi Okabe as Dr. Tabata's Assistant (uncredited)

Toranosuke Ogawa as President of Company (uncredited)

Frank Iwanaga as Security Officer Tomo Iwanaga (uncredited)

Mikel Conrad as George Lawrence (uncredited)

Kokuten Kōdō as The Old Fisherman (uncredited)

Kenji Sahara as Man on Boat (uncredited)

Haruo Nakajima as Godzilla (uncredited)

Katsumi Tezuka as Godzilla (uncredited)