Boog (Chris Williams) is a 900-pound grizzly who is the star of the town of Timberline's nature show. In a dream, Boog pursues a giant version of his teddy bear Dinkleman, but he is soon woken by Beth (Kari Wahlgren), who takes him to the town center for Boog's performance. But Beth finds that Shaw (Darryl Kurylo), a cruel hunter, has already hunted a buck. She goes into the police office of her best friend, Sheriff Gordy (Carlos Alazraqui), to confront Shaw. The buck wakes up and introduces himself, his name being Elliot (Maddie Taylor). Boog reluctantly frees him, and Shaw vows revenge on Boog after Gordy tells him he's been living in the woods too long. That night, Elliot decides to "free" Boog in return. He manages to lure him to the convenience store, where they finish all the chocolate bars there, but they're discovered by the police and incapacitated with a tranquilizer gun by Beth and brought to the Timberline National Forest until the start of open season. There, Elliot claims that he knows how to get back to Timberline, prompting a road trip.
They encounter a squirrel called McSquizzy (Michael Gough) and his army of squirrels called the Furry Tail Clan (Carlos Alazraqui), who abuse them with nuts. Boog meets a few members of Elliot's herd: Giselle (Kari Wahlgren), a doe whom Elliot has a crush on, and Ian (Patrick Warburton), the head of the herd who hates Elliot. It's revealed that during this time of year, the Deer Games are held, with only one sport: Running. Elliot competes with Ian and wins the race, but he's kicked away by a jealous Ian as revenge. In the Timberline National Forest, Boog and Elliot help all kinds of animals with their tasks. The two meet McSquizzy again, who directs them to a shortcut: A mine. After riding through the mine in a minecart, Boog and Elliot continue their journey across a valley, and climb up a mountain, only to encounter Shaw, they escape the hunter by rolling down the hill in a big snowball. They get to a beaver's dam, which Elliot claims is the way home. Not letting them cross, the two help the beavers find a missing piece for the dam: An outhouse. They find Boswell (Maurice LaMarche), trying to push the outhouse down from a hunting camp. Boog and Elliot jump onto it, and it quickly breaks and they ride it down the river rapids until they reach the dam. Boog quickly realizes that Elliot had never known how to go to Timberline because he'd asked some moles (since they're blind) for directions. Boog's weight causes the dam to break up. Having lost Elliot in the flood, Boog looks for shelter for the night. Boog enters Shaw's house, only to be confronted by Shaw himself. Shaw locks Boog in his basement but Boog eventually escapes, and encounters McSquizzy on a sign, who threatens to not show him the way back home if he doesn't help the animals during open season. Boog goes the right way, but he decides to go back and help the animals, suggesting to the wilds that they fight back.