Things couldn't be much better for Boog the grizzly bear (voice of MARTIN LAWRENCE). Living in the garage of park ranger Beth (voice of DEBRA MESSING), he's surrounded by all sorts of creature comforts and is something of a celebrity in the wooded town of Timberline where he performs on stage with his caring owner.
However, not everyone is a big fan, especially aggressively uptight Shaw (voice of GARY SINISE) who's gotten an illegal jumpstart on the hunting season by bagging himself a buck. Yet, Elliot (voice of ASHTON KUTCHER) -- who's tied to the hood of Shaw's truck -- is only dazed after being run down by the hunter and begs for Boog to help. He reluctantly does, thus enraging Shaw.
It seems Elliot has been kicked out of his herd by alpha male Ian (voice of PATRICK WARBURTON) who doesn't want any competition from the scrawnier deer in hopes of wooing doe Giselle (voice of JANE KRAKOWSKI). Accordingly, Elliot wants to hang out with Boog, but his hyperactive ways soon have the grizzly reacting adversely, thus horrifying the townsfolk. As a result, Beth begrudgingly and tearfully must return him to the wild, unaware that he has no idea how to survive there.
Still accompanied by Elliot who continues to annoy him, Boog tries to get the lay of the land, but ends up confronting militant squirrel McSquizzy (voice of BILLY CONNOLLY) and his band of synchronized rodents, as well as beaver foreman Reilly (voice of JON FAVREAU) who isn't happy when the huge bear inadvertently breaks his dam and washes all of the animals downstream. As they end up in the area's hunting grounds just as open season begins, Boog and the others must figure how to avoid being shot, especially by Shaw who wants to get revenge on the bear for freeing Elliot.