Inventor Goro Ibuki
Hiroshi Jinkawa
Rokuro 'Roku-chan' Ibuki
Japan Special Defense Forces Chief
Lead Seatopian Agent
Seatopian Agent
Truck Driver's Assistant
Man from Unit 1
Emperor Antonio of Seatopia
Truck Driver
Antonio's Aide (Radio Operator in White)
Godzilla
Megalon
Jet Jaguar
Jet Jaguar
Gigan (as Kengo Nakayama)
Emperor Atonio of Seatopia (voice)
Narrator
Godzilla (archive footage) (uncredited)