Continuity mistake: After Koda frees Kenai from the rope trap, the rope disappears twice from around his (Kenai's) leg: first when he is walking towards his brother Denahi (then the rope reappears around his leg as he runs away), and disappears again when he meets Koda again inside the glacier (only to reappear again when he snags it around a rock/ice chunk and trips).
Other mistake: At the end of the film, as Kenai walks up to Koda after he's been transformed back into a bear, Koda leaps on him in joy. If you look closely at Kenai's hind legs, there are a few frames of animation missing. His legs go from a standing to a sitting position instantly. It's barely noticeable (no pun intended).
Factual error: During the opening scene when Kenai is running away from a herd of stampeding caribou, several of the caribou do not have antlers, even though both male and female caribou sport antlers. One of these "antlerless" caribou is even seen running near the front of the herd and is easy to see.