Thorin is the leader of the dwarves, and he takes himself very seriously. He is conscious of his position as son of Thrain and grandson of Thror, King under the Mountain, and mindful of his birthright to the treasure trove guarded by Smaug. He retains this sense of self throughout the journey until, in Chapter 8, he is captured by elves and imprisoned in the palace of the Elvenking. At this point, Bilbo assumes the role of leader, freeing Thorin and the other dwarves when they could do nothing to effect their own release.

Thorin is brave and intelligent and his leadership of the dwarves is unchallenged; Kili and Fili are especially loyal to him and eventually die with him in the Battle of Five Armies. He makes a mistake, however, when he refuses to parley with Bard on the eve of the battle. His intense desire for the treasure, typical of the dwarf love of beautiful material things, and his refusal to reconcile with the elves are contributing factors to that war. When he dies of wounds suffered in the Battle of Five Armies, he is buried with the Arkenstone, a gesture of love but also of the futility of battling for property.