 Katsuhiko SasakiInventor Goro Ibuki | Inventor Goro Ibuki |
 Yutaka HayashiHiroshi Jinkawa | Hiroshi Jinkawa |
 Hiroyuki KawaseRokuro 'Roku-chan' Ibuki | Rokuro 'Roku-chan' Ibuki |
| KKanta MoriJapan Special Defense Forces Chief | Japan Special Defense Forces Chief |
 Kotaro TomitaLead Seatopian Agent | Lead Seatopian Agent |
| UUlf OtsukiSeatopian Agent | Seatopian Agent |
| SSakyo MikamiTruck Driver's Assistant | Truck Driver's Assistant |
| FFumiyo IkedaMan from Unit 1 | Man from Unit 1 |
 Robert DunhamEmperor Antonio of Seatopia | Emperor Antonio of Seatopia |
| GGentaro NakajimaTruck Driver | Truck Driver |
| RRalph JesserAntonio's Aide (Radio Operator in White) | Antonio's Aide (Radio Operator in White) |
| SShinji TakagiGodzilla | Godzilla |
| HHideto OdachiMegalon | Megalon |
| TTsugutoshi KomadaJet Jaguar | Jet Jaguar |
| MMasachika MoriJet Jaguar | Jet Jaguar |
 Kenpachirō SatsumaGigan | Gigan |
 Gorō NayaEmperor Atonio of Seatopia (voice) | Emperor Atonio of Seatopia (voice) |
| EEisuke NakanishiNarrator | Narrator |
 Haruo NakajimaGodzilla (archive footage) (uncredited) | Godzilla (archive footage) (uncredited) |
| KKôetsu ÔmiyaAnguirus | Anguirus |
| TTeruo NigakiRodan | Rodan |
| EEisaburo KomatsuNot listed | Not listed |
| EEisuke NakanishiNot listed | Not listed |
