Michael Keith as Eric Carter

Harry Holcombe as Dr. Arnold Johnson

James Yagi as Yutaka Omura

Tadao Takashima as Osamu Sakurai

Kenji Sahara as Kazuo Fujita (as Keji Sahaka)

Ichirō Arishima as Mr. Tako (as Ichiro Arishima)

George Takei as Osamu Sakurai (voice) (uncredited)

Les Tremayne as Mr. Tako / Dr. Shigesawa / Dr. Akira Makino / General Masami Shinzo / Commander Roberts / Narrator (voice) (uncredited)

Byron Morrow as Newscaster (uncredited)

Mie Hama as Fumiko Sakurai (uncredited)

Akiko Wakabayashi as Tamiye (uncredited)

Akemi Negishi as Chikiro's Mother (Dancing Girl) (uncredited)

Akihiko Hirata as Dr. Shigezawa (uncredited)

Yū Fujiki as Kinzaburo Furue (uncredited)

Jun Tazaki as General Masami Shinzo (uncredited)

Yoshio Kosugi as Faro Island Chief (uncredited)

Ikio Sawamura as Witch Doctor (uncredited)

Kenzō Tabu as Dreary Newscaster (uncredited)

Tatsuo Matsumura as Dr. Akira Makino (uncredited)

Victor Millan as Rodrigo Infanta (uncredited)

Douglas Fein as Commander Roberts (uncredited)

Haruo Nakajima as Godzilla (uncredited)

Shōichi Hirose as King Kong (uncredited)

Katsumi Tezuka as Godzilla in iceberg (uncredited)

Paul Mason as Misc. Characters (voice) (uncredited)

Bruce Howard as Misc. Characters (voice) (uncredited)