Long ago in a post-ice age North America, there are three Indian brothers named Kenai, Denahi, and Sitka. Denahi is the middle brother, and Sitka, the oldest. Kenai, the youngest, hates bears because they fight for the same food, overtake the land, and ruin his coming-of-age ceremony. Each brother was given his own totem when they came of age: Sitka, the eagle of guidance and Denahi, the wolf of wisdom.
Kenai receiving his totem.At the ceremony, Kenai is presented with the bear of love. Kenai questions the totem he has been given with his brother by saying that "[bears] don't love anyone, they don't think, they don't feel [...]", calling them thieves when he notices the stolen fish basket.
When Sitka is killed in a battle with the bear that stole the basket, Tanana, the tribal shaman, officiates a funeral rite for Sitka. Suddenly Kenai ignores the village teachings of brotherhood with animals and sets out to hunt the bear for revenge and eventually kills it. To punish Kenai, the Great Spirits, represented by the spirit of Sitka, transform him into a bear. Unfortunately his other brother, who was pursuing Kenai to stop him, doesn't realize what has happened. He finds Kenai's torn clothes and believes the bear took his other brother's life. In grief, he vows revenge.
Disoriented and barely escaping Denahi's wrath by falling into the river, Kenai awakens on the shore and in the presence of Tanana, who eases him through his initial shock at his change. Although she cannot understand his bear speech, she advises Kenai to find where the lights touch the mountain so that he can ask Sitka's spirit to change him back, and then she disappears without giving him directions. To Kenai's surprise, he finds he can talk with the other animals - but the only animals who are willing to talk to him are two stupid sibling moose, Rutt and Tuke, who are more interested in cracking jokes at Kenai's claims to be a man than helping him. Along the way, Kenai meets a talkative, pesky bear cub named Koda, who claims to know the way to the salmon run where the bears gather to fish and where the lights seem to hug the mountain.
What follows is a journey in which Kenai, when not dodging Denahi who is now hunting him, grows rather fond of the irrepressible Koda who he learns shares his spiritual beliefs. This in turn puts his hatred of bears in a stark perspective that forces him to reconsider, especially when he learns that Koda sees humans as the same sort of dangerous monsters as he himself once believed bears to be. This culminates when they finally reach the salmon run and Kenai has the awkward experience of being surrounded by bears. Yet, the bears quickly accept him and he in turn learns about the loving community of these animals that makes his hate seem so foolish even as he learns to enjoy himself.