The premise of the show is the evil Garoga aliens plan to take over Earth with their army of giant Fearbeasts. They are opposed by the members of a family from a planet called Peaceland that was also destroyed by Garoga. They use a variety of exotic vehicles and weapons but their primary weapon against Garoga is the oldest child Hikaru, who is able to transform into the giant Zone Fighter.
Godzilla was being portrayed as more or less a kaiju superhero at the time and helped Zone Fighter battle evil monsters created by the show's villains. At times they were even shown having friendly mock combat with one another.
King Ghidorah's origin is changed, the show's villains saying they created him. He was unique for the show because he managed to escape from Zone Fighter without being killed.
Gigan also appeared in the show but did not share King Ghidorah's luck; he was dramatically killed by Zone fighter's missile might bracelets.
The Sakimori/Zone family resembles a normal Japanese family, but they are an alien family that came to Earth after their home planet Peaceland was destroyed by the evil Garoga aliens. To stop the Garoga army's invasion on Earth, the Sakimori family's three children, Hikaru (the oldest son), Hotaru (the teenage sister) and Akira (the young boy) transform into the superheroes Zone Fighter, Zone Angel and Zone Junior. Their transformation code (associated with a "henshin" pose) is "Zone Fight Power".
- Hikaru Sakimori/Zone Fighter is the oldest of the siblings. He works as a test driver for cars. As Zone Fighter, upon uttering the command "Zone Double Fight", he can also grow to giant size (with a streamlined metallic head) to fight the Garoga's Fearbeasts. His killing attack is the meteor proton beam where he shoots a monster with missiles mounted on his wrists. Just like Ultraman, he can only become giant sized for a limited time, and the meter light on his belt buckle changes from green (normal) to yellow (caution) to red (danger). Zone Angel and Junior can recharge Fighter's energy with the emergency battery from Smokey. He was played by Kazuya Aoyama.
- Hotaru Sakimori/Zone Angel is the second oldest of the siblings. She attends high school. She was played by Kazumi Kitahara.
- Akira Sakimori/Zone Junior is the youngest of the siblings. He attends grade school. He was played by Kenji Sato.
- Yoichiro Sakimori is the father of the three children. He is the proprietor of the Toy Research Institute, which explains the family's penchant for toys. He invents the gadgets and vehicles used by the Zone siblings to fight the Garoga army. He was played by Shoji Nakayama.
- Tsukiko Sakimori is Yoichiro's wife and the mother of the three children. She was played by Sachiko Kozuki.
- Raita Sakimori/Zone Great is Yôichirô's father and the grandfather of the three children. When his grandchildren are in a terrible predicament, he uses the Great Raideki satellite to get them out of trouble. He was played by Shiro Amakusa.
- Godzilla appears in the series as a close ally of the Zone family, often coming to Zone Fighter's aid. He maintains his traits, and is also a fast runner. For the series, the MegaroGoji suit was used, fresh from Godzilla vs. Megalon.