In DragonBall Z, Goku has is an adult and has a son Gohan. However, hordes of evil warriors appear threatening his new family. First are the saiyans, a blood-thirsty race which specializes in genocide and mass destruction. A Saiyan named Radditz claims to be Goku's brother and tries to blackmail him into killing innocent Earthlings by kidnapping Gohan. True to his good nature, Goku sides with his adoptive planet and takes shocking actions to ensure the safety of both his son and the people of Earth. One year later, the Saiyans continue their assult when Prince Vegeta and his sidekick Nappa arrive, intent on retrieving the DragonBalls to wish for immortality. Although they are eventually defeated, several of his friends are lost in the melee.

After recuperating from the fight with Vegeta, the DBZ warriors head off to the planet Namek to gather the "Namek Dragonballs", planning to wish their fallen friends back to life. There they encounter Freeza, a mercanary alien who destroys all life on entire planets and sell the vacated space to the highest bidder.

It is on this shattered world that Goku's destiny as the legendary "Super Saiyan" is revealed, as he makes the ultimate sacrifice to protect his friends and the universe. However, it is not until the appearance of a mysterious and powerful teenager named Trunks that Freeza is finnaly stopped.

Other evil warriors such as Cell and Buu come to rein their terror against the Earth, the Earth's warriors are there to stop them and the Earth is peaceful once again.