He was voiced by the late Jason Raize.
Denahi is the older brother of Kenai and younger brother of Sitka. He often likes to tease Kenai.
One day, after Kenai gets his bear totem, Denahi starts to tease him about it. When a bear steals a basket full of fishes, he orders him to get it back, much to Sitka's chagrin. Kenai is attacked by a bear and the two start helping him. However, in the battle, Sitka is weakened by the bear, and makes a heroic sacrifice, but the bear did not die.
In that night, Kenai suggest to get revenge on the bear, but Denahi refuses to follow his orders because killing the bear is a wrong thing to do. He decided to stop the former from his doing.
So, in the next morning, Denahi witnesses Kenai battling the same bear. By the time he got there, Denahi sees Kenai's torn clothes and thinks the bear killed him (unknown to him that the bear is Kenai as he was just transformed into one by the spirits). He swears revenge afterwards.
Later, Denahi tries to kill Kenai, not recognizing him as a bear. He appears again trying to get him and Koda in the lava, but fails again. As time goes by, Denahi's anger slowly descends into madness and fury. He grows a goatee and mustache to further portray him as a villain.
Denahi appears in the mountains trying to kill Kenai again, but Koda arrives to save him. Kenai tries to save him, but as Denahi is about to deal him with the same killing blow Kenai did earlier, Sitka turns him back into his human self with Denahi and Koda witnessing it. Kenai says that the latter really needs him, so Denahi, having finally realized his errors, fixes them by stating that he really liked him as a bear better. Kenai is initially worried about becoming a bear again, but Denahi reassures him that he will be still his little brother no matter what and accepts his younger brother's fate. Kenai is turned back into a bear, and he, Denahi, and Koda play for a while before going back.
The end reveals that Denahi is the old man narrating the story to a group of children.
- In complete contrast to Judge Claude Frollo, Scar and Lots-O' Huggin' Bear (among others), Denahi is easily one of (if not the) most sympathetic villains ever to appear in a Disney film, to the point that there's been some debate as to whether he can be considered a villain at all.
- He is most likely an anti-hero or, at the very most, an anti-villain, as all he truly wanted was to avenge Kenai's death, unaware of the fact that the bear he was pursuing WAS Kenai. And the second he realized the error of his ways, he instantly let go of his anger and reverted back to his good-natured self. Nevertheless, due to the fact that there is no other antagonist in Brother Bear, he is the closest thing the film has to a villain.
- Denahi is similar to Jack Torrance; they start out as good guys (clean-shaven), but as time goes on, they slip into insanity and evil and grow facial hair to reflect this.