This story is based on the popular Japanese manga cartoons created by Akira Toriyama. The movie begins with a legend. Lord Piccolo (James Marsters) wishes to rule the earth. In doing so, he will destroy it. A group of warriors band together and bind Lord Piccolo into the earth. They use seven magic dragonballs, which are then distributed throughout the world.

Goku (Justin Chatwin) lives with his grandfather (Randall Duk Kim), who is training him to be an expert in martial arts. Like all true fighters, Goku is told not to rely on his external senses but to rely on what is inside him – to use his ‘ki’. On Goku’s 18th birthday, his grandfather gives him a dragonball. Goku is happy to have it but it does not mean much to him. Goku never knew his parents but at his 18th birthday dinner, his grandfather will tell him what really happened to them.

At school, Goku is considered a geek and a weirdo, but he is very keen on Chi Chi (Jamie Chung). When he gets to school, his bike is run over by one of a group of ‘cool’ boys who bully him. When he does not fight back, it is seen as proof that he is scared. In fact, Goku has promised his grandfather he will not fight ‘boys’. Later on, when Chi Chi cannot open her locker, Goku helps her by using his ‘ki’. He tries to hide but she sees him and is impressed, and appears to understand how he did this. She invites him to her party.

Every year, Goku and his grandfather celebrate his birthday together. This year, however, he goes to Chi Chi’s party (without telling his grandfather) and at the last minute takes the dragonball with him. Once he gets there he is again bullied, but this time he fights back. While this is happening, Lord Piccolo descends on Goku’s grandfather’s house. When he finds the dragonball missing, he attacks Goku's grandfather and destroys the house. Goku feels that there is something wrong and races back to find his grandfather buried in the house. Just before Goku’s grandfather dies, he tells Goku that Lord Piccolo has returned and that Goku needs to find Master Roshi and the other dragonballs to defeat him. Goku is very sad and guilty that he was not there to help his grandfather.

Goku decides to pursue Lord Piccolo to avenge his grandfather’s death. On the way, he is helped by Bulma (Emmy Rossum), who has invented a dragonball tracker after her father’s dragonball was stolen (also by Lord Piccolo). She hopes to get it back and use it as a form of energy. Together, Goku and Bulma find Master Roshi (Chow Yun Fat) and are joined by a charismatic thief called Yamcha (Joon Park). These four work together to track the dragonballs.

While this is happening, Goku’s romance with Chi Chi develops and she tries to help him improve and perfect his fighting skills. He eventually comes face to face with Lord Piccolo. Only by being true to himself and remembering his training can Goku hope to defeat Lord Piccolo.