Heihachi was born as the heir to the rich, powerful, and well-respected Jinpachi Mishima, the owner of the powerful Mishima Zaibatsu and a world-famous martial arts master. During this time, Heihachi married Kazumi and eventually had a son with her named Kazuya Mishima. It is believed that his wife Kazumi died while giving birth to Kazuya or not long afterward. Heihachi raised Kazuya harshly. Much to his chagrin, Kazuya grew up kind and frail, perhaps due to the more loving treatment he received from his grandfather Jinpachi (see Kazuya's Tekken 5 ending). At some point, Heihachi betrayed Jinpachi and stole the Zaibatsu from him. His motives for this act are as-of-yet unknown, but it can be speculated that Heihachi disagreed with his lack of aggression and his "soft" treatment of Kazuya. After assuming control, Heihachi began to steer the Zaibatsu into the military industry. Jinpachi attempted to launch a coup to retake the Zaibatsu from his son, but failed and was ultimately imprisoned underneath Hon-Maru where he remained for 40-45 years until the events of Tekken 5.

During the King of Iron Fist Tournament 6 (which he secretly entered), he was defeated by Lars, who is later revealed to be his illegitimate son.