In the mid-1860s, an English couple and their infant son are shipwrecked off the Congolese coast. The couple builds a treehouse but are killed by Sabor, a vicious leopardess. Kala, a female gorilla who recently lost her own child to Sabor, finds the human infant and takes him back to the jungle to raise as her own, despite the disapproval of her mate, Kerchak, who is also their group’s leader. Kala names him Tarzan. He has the ability to hear animals speak English, despite that other humans only hear normal animal sounds.
Years later, Tarzan has befriended other animals, including a young female gorilla named Terk and the paranoid male elephant, Tantor. Tarzan finds himself treated differently by the gorillas because of his appearance, making great efforts to improve himself and fit in with them. As a young man, Tarzan manages to kill Sabor, gaining Kerchak’s reluctant respect.
The gorilla troop’s peaceful life is interrupted by the arrival of a group of human explorers from England, consisting of Professor Porter, his daughter, Jane, and their hunter-guide Clayton. The explorers are looking to study gorillas. Jane accidentally becomes separated from the group and chased by a baboon troop, with Tarzan saving her. He recognizes that she is human, just like he is. Jane leads Tarzan back to their camp, where Porter and Clayton both take great interest in him. Despite Kerchak’s warnings to be wary of the humans and stay away from them, Tarzan continues to return to the camp, where Porter, Clayton, and Jane teach him to speak English as well as what the human world is really like; he and Jane also begin to fall in love. However, they have a difficult time convincing Tarzan to lead them to the gorillas due to his fear of betraying Kerchak’s trust.
The explorers’ ship soon returns to retrieve them. Jane asks Tarzan to return with them to England, but Tarzan asks Jane to stay with him when Jane says it is unlikely they will ever return. Clayton convinces Tarzan that Jane will stay with him forever as long as he leads them to the gorillas. Tarzan agrees and leads the trio to the nesting grounds while Terk and Tantor lure Kerchak away. Porter and Jane are excited to mingle with the gorillas, but Kerchak returns and attacks them. Tarzan holds Kerchak back while the humans escape. Kerchak accuses Tarzan of betraying the troop, making him feel conflicted and isolated. Kala takes Tarzan to the treehouse where she found him, shows him his true past, and says that she wants him to be happy whatever he decides. Tarzan puts on a suit that once belonged to his father, signifying his decision to go to England.
When Tarzan boards the ship with Jane and Porter the next day, they are all betrayed by Clayton and his team of stowaway poachers. Now that he knows where the nesting grounds are, Clayton plans to seize the gorillas and return with them to England to sell them and locks Tarzan, Jane, and Porter away to prevent them from interfering.
Back in the jungle, Clayton and his men attack the gorillas. They attempt to fight back but are quickly overpowered. However, Tarzan manages to escape the boat with Terk and Tantor’s help, and he returns to the jungle, where he and his friends defeat Clayton’s men and free the imprisoned gorillas. Clayton shoots Kerchak and battles Tarzan across the treetops, although Tarzan spares his life and smashes his shotgun. Clayton attempts to free himself from vines with his machete but falls from the tree with a vine tangled around his neck, hanging and killing him. Kerchak, with his dying breath, apologizes to Tarzan for being resentful towards him, finally accepts him as his son, and names him the new leader of the gorillas.
The next day, Porter and Jane prepare to leave on the ship while Tarzan stays behind with the troop. As the ship leaves shore, Porter encourages his daughter to stay with the man she loves, and Jane jumps overboard to return to shore; Porter shortly follows her. The Porters reunite with Tarzan and his family and embark on their new life together.