Alien invaders take over Great Mazinger who is at the entrance of a museum next to Mazinger Z as symbols of peace. Grendizer fights the evil invaders and Great Mazinger is recovered. When the Vegan empire dispatches a new general to oversee the takeover of Earth, he quickly manages to capture Koji Kabuto and, learning of Great Mazinger through interrogation, quickly commandeers it from a museum where it was kept as a symbol of peace. It is now up to Duke Fleed aboard Grendizer to stop humanity's former defender from becoming its destroyer.
| Release Date | March 20, 1976 | |
|---|---|---|
| Status | Released | |
| Original Title | UFOロボ グレンダイザー対グレートマジンガー | |
| Runtime | 24min | |
| Budget | — | |
| Revenue | — | |
| Language | Japanese | |
| Original Language | Japanese | |
| Production Countries | Japan | |
| Production Companies | Dynamic PlanningToei Animation | |
