Johnny "Pono" Kapahala, a teen snowboarding champion from Vermont, returns to Oahu, Hawaii, for the wedding of his grandfather, local surf legend Johnny Tsunami. He is excited for his grandpa to get married as he anticipates finally getting an uncle to hang out with. As soon as he comes, he meets up with his old friend, Sam who moved to Hawaii from Iceland after four years. He gets excited to hang out with his new uncle until he realizes his "Uncle Chris" is the 12 year old bratty kid his grandpa was teaching to surf, but Johnny remains determined to get Chris to like him.
The Dirt Devils tell Chris to do a dangerous ride down a large sanddune on illegal property but gets caught by the police and kicked off. Chris is banned from dirt boarding further straining his relationship with Johnny.
The next day, Sam and Johnny catch Chris heading off with the Dirt devils. They follow him to a barge set up with a skate park. But before Chris can skate, Johnny and Sam show him up by skating the barge. Annoyed, Chris runs away and when he gets home gets into a fight with Johnny and tells him to leave him alone. So, the next morning, Johnny's grandpa lets him go off and surf. He bumps into Val and gives her a surfing lesson, making Chris jealous and upset. Forced to hang out with Chris, Johnny and Sam blackmail him into coming along with him for a day. With Val, they go dirtboarding, ride ATVs, and to Chris' surprise, have a good time and Johnny and Chris finally start getting along.
The group headed out to a dirt boarding event to meet Akoni Kama and possible sponsors but they kicked Val out of the Dirt Devils for hanging with Johnny and Chris, the "competition". Johnny and Sam, who were looking for Chris who had run away from home, drove to the event with Val, to find Chris fighting with Jared on when he could join the Dirt Devils. He agrees to do a dangerous jump the next day during the rehearsal dinner for Carla and Johnny's wedding and the night before the opening of the shop.
Though Johnny tells him that he isn't allowed to go to do the jump, he tricks Johnny into think he has changed and comes along with him into town to get items for the rehearsal dinner that night, but runs away to find the Dirt Devils. By the time Johnny finds him, he does the jump- and ends up with a broken arm/wrist. They go back home and begin to set aside their differences and get along, when they got news of a break-in at the shop. The store was trashed. Jared is immediately arrested after he is found with a bag of broken gear from the shop. Troy comes over and denies being involved in the break-in. He then tells Chris that he is fit to join the Dirt Devils, but both Johnnys say no. Chris runs away saying that he hates the family, leaving Carla feeling guilty about bringing him along.
Carla decides to move back to Pennsylvania in a conversation with Johnny's Grandpa, which Chris overhears. He feels guilty about causing their break-up, but doesn't know how to mend it. Johnny then says that he is lucky he has a smart nephew and tells him to follow him. Eventually with help from Val, Sam and Johnny he fixes the surf shop and decides to stop hanging with the Dirt Devils. Then at the opening, the store becomes a huge success, with even pro-dirt boarder Akoni Kama coming.
Meanwhile across the street at the Dirt Devils, they find Troy in a heated argument with Val's dad over negotiations breaking down on condos being built for him to move to California, leaving the Dirt Devils and over him supplying for Johnny and Carla's shop. Even the Dirt Devils, betrayed and angry, turn on Troy. He then gets into a fight with Johnny's grandpa over who can sell dirt boards in their shop. Johnny, realizing that he's never seen the "godfather of dirtboarding" ride before tells him to be quiet and eventually challenges him to a mountain boarding race to see who can sell the dirt boards. If Johnny wins, they can both sell them and if Troy wins, he can sell them.
Johnny and Chris finally reach terms of friendship and he helps him with the race, by describing the course set up by Val's father so the Dirt devils could mountain board safely and legally. The race begins with Troy in the lead for a large portion of the time, until the ending when he falls when doing one of three required tricks and Johnny wins the race, and crashes into the barrier at the finish line. Carla and Johnny finally decided to get married and both Johnnys get a new friend.
Brandon Baker as Johnny "Pono" Kapahala
Jake T. Austin as Christopher "Chris"
Cary-Hiroyuki Tagawa as Grandpa Johnny "Tsunami" Kapahala
Robyn Lively as Carla
Mary Page Keller as Melanie Kapahala
Yuji Okumoto as Pete Kapahala
Lil' J as Sam Sterling
Andrew James Allen as Jared
Rose McIver as Valerie "Val"
Phil Brown as Troy
Nick Jonas as Writer
Akoni Kama as himself
Thomas Newman as Bo
Fasitua Amosa as Officer
William Wallace as Officer
Mountainboarding stunts performed by:
The DVD was released on October 9, 2007.