An armada of horned humanoid aliens known as Boazanians invade earth and launch their "beast fighters" all over the world, defeating most of the world's armed forces. The Boazanians first defeat from the hands of Super Electromagnetic Machine Voltes V brings the invaders to focus their attacks on Japan. Voltes V was designed by Professor Kentaro G? (Doctor Ned Armstrong), his wife Professor Mitsuyo G? (Doctor Mary Ann Armstrong) and their trusted colleague, Professor Hamaguchi (Doctor Richard Smith) and built by large scale construction effort backed by United Nations Earth Defense Force and General Oka (Commander Robinson). Voltes V is a robot composed of five "Volt Machines", and each are themselves formidable weapons. Each machine is piloted by Ken'ichi (Steve), Daijiro (Big Bert), and Hiyoshi (Little Jon): the three sons of Kentaro and Mitsuyo G?, along with the only daughter of General Oka; Megumi (Jamie Robinson), and Ippei Mine (Mark Gordon), an orphan cowboy.

Thousands of years ago, the people of the planet Campbell decided to leave their planet and seek out new worlds to inhabit. One group, lead by the scientist Oreana, landed on Earth, but was delayed from their mission. In the early 21st century, Oreana's group reawakens and begins their plan to conquer the Earth. The only effective defense against the Campbellians' giant biomechanical slave beasts is the super-electromagnetic robot, Combattler V and its pilots.