The son of Bella Swan's father's friend, Billy Black. Bella uses me to get information on Edward Cullen and his family, I tell her Quileute legends and introduces her to the idea that Edward is a vampire. Bella comes to like Jacob, and he develops a crush on her.

After months of depression over Edward's leaving, Bella finds friendship with me and slowly begins to come out of her depression. Our friendship becomes very strong, and I also develops romantic feelings for Bella that she does not reciprocate. Jacob is also one of an ancient line of werewolves, a member of the Quileute tribe that has forever been the mortal enemy of vampires. Jacob undergoes his first transformation into a wolf in response to a new vampire threat, and he becomes busy patrolling the forest with his pack, searching for vampires in the area. When Bella is caught by the vampire Laurent alone in a clearing, she is saved by Jacob and the pack, who manage to destroy Laurent.

Bella, who has been taking risks to feel closer to Edward, impulsively jumps off a cliff and almost drowns, but Jacob saves her life. After Edward mistakenly believes Bella to have died, she and his sister, Alice, rush to Italy to stop Edward from killing himself, leaving Jacob hurt and angry. Jacob is disgusted by Edward's return and by Bella's willingness to take him back after he left her; he is also outraged when he learns of Bella's desire to become a vampire. Jacob reminds Edward of his tribe's treaty with the Cullen family, which states that the Cullens are not allowed to bite any humans.