In the original movie, Tarzan starts off as a baby who escapes a burning ship with his biological parents and lives in a treehouse built by them as a happy family. Tragedy falls upon the new family, however, as his parents are killed bySabor the Leopard later on (Two Worlds). Luckily, the baby is rescued by a female gorilla named Kala who had lost her baby gorilla son to Sabor. After escaping Sabor, Kala brings the baby back to her gorilla family and tells her mateKerchak, the leader, that she wants to adopt the baby since his parents were killed by Sabor and there are no more humans left in the Jungle, to which Kerchak agrees but says that the baby won't be his son. Kala names the baby, Tarzan, and sings him a lullaby about being in her heart forever.
A few years later, Tarzan grows into a boy and likes to tag along with his best friend, Terk and some other gorillas. One day, while tagging along, Terk jokingly tells Tarzan to get an elephant hair off an elephant tail while Terk is busy with some other gorillas hoping to keep him away, to which Tarzan takes seriously and, unfortunately, jumps into the water and swims up to an elephant and grabs its tail causing the elephants to run wild and rush through the gorillas' territory. When Kerchak sees this, he scowls at Tarzan, who survived the stampede, met and befriended a young elephant named Tantor, and actually got the elephant hair, telling him that he will never be one of them. Disappointed and hurt by this, Tarzan runs down to the edge of the water and puts mud all over himself and then Kala shows up at night. Tarzan is encouraged by Kala that he's "not that different" at all.
During his entire teenage years, he grew up with continuous struggles to fit in with the gorillas; performing various monkey-like action and other animal actions such as picking fruit, learning other animal languages, fighting a snake, eating termites, etc.
One day, as he is playing with Terk and Tantor, he hears a noise in the bush. As he comes close, it turns out to be Sabor. Kerchak fights and is injured by the leopard. Tarzan fights the leopard, and get scratched on the heart in the process, but lives. Tarzan steps in and kills the leopard with Kala, Kerchak (in a way), Tantor, Terk, and the entire gorilla pack cheering for his victory. He then presents Kerchak Sabor's corpse earning his reluctant respect.
Almost instantly later, they hear a loud noise in the forest. While the other gorillas (and Tantor) run away, Tarzan-driven by his curiosity-decides to figure out the noise, which turns out to be a gunshot fromClayton-who is the bodyguard of the gorilla explorers pack of Jane Porter and her father, ProfessorArchimedes Q. Porter. Fascinated by them, due to the fact he's never seen another human being before, Tarzan spends some time (possibly a while) to spy on them without being noticed.
Later, Jane is drawing a picture of a baby baboon, the baboon likes it and takes it from her. When she tricks him to give the picture back, his crying angers a huge pack of baboons. Luckily, Tarzan comes to the rescue. After a number of events, when they're safe on the tree, Tarzan settles the chase, which is the first time the viewers saw the movie from the human angle (as the scene showed he was able to communicate with the baboons) by returning the drawing to the baby baboon. As Jane tries to leave, it's raining and they are forced into the shade of the big tree. When on the tree, he shows an extremely curiosity by her, does various of weird action (listens to her heartbeat, tickles her, touches her hand...). Finally, he has the ability to talk human as he said his name "Tarzan" (although how is not clear, as this name was given by Kala, which means, despite his parents could teach him English before they were killed, he logically can't say his name in English). After it stops raining, he carries Jane back to her camp. When Terk, younger gorillas, and Tantor are trashing the camp while making music, Tarzan steps in and solves the problem. Unfortunately, Kerchak appears and tells everyone to come back. Later, Kerchak warns everyone and Tarzan about the danger of humans. However, Tarzan disobeys and keeps returning to the camp.
In the next morning, he jumps between Jane and Clayton's argument. Clayton, Jane and her father realize he is the perfect person to help them which their research. They teach him about human behaviors, English, as well as thing he's never seen before (city, astronomy...). During this time, he's starting to fall in love with Jane. Although he refuses to lead the explorers to the gorilla nest, concerned about their safety. His affection towards Jane and weird actions (riding a bicycle, leaving early in the morning...) leave Kala and Terk concerned and feel left out.
As the explorers, unfortunately, are starting to return to England, Tarzan displays hurt, to one point even tries to convince Jane to stay with him. However, Clayton uses this situation as an advantage to his plans and misleads Tarzan into thinking that Jane would stay if he showed them the gorillas. Tarzan agrees and leads the party to the gorilla pack's home, while Terk and Tantor lure Kerchak away to avoid having him attack the humans. Jane and her father are excited to mingle with the gorillas. However, Kerchak returns and tries to attack them. Tarzan stops him to let the explorers to run away.
Kerchak confronts Tarzan's actions, telling him that he has betrayed his family. While Tarzan's sitting on a tree, Kala comes near him and he expresses his confusion. Kala leads him to the old treehouse, tells him that she should've told him about it long ago and that she isn't his biological mother. He realizes that he was a human all along and, after Kala said that she'll be happy whatever makes him happy, dresses in his father's suit and follows the explorers to England. Before leaving, he says to Kala: "No matter where I go, you'll always be my mother."
When he's on the ship, he is surprised to find that Clayton's men had captured the crew and that they were doing the same with Archimedes and Jane. The thugs try to capture him, but thanks to his agility he manages to avoid them by jumping on the cages and climbing the ship's mast. However, they weren't exactly slow, as one of them manages to grab him from his ankle and leave him hanging from the mast. After shaking him off, and seeing the rest of the thugs closing in on him, he makes a huge leap from the top of the mast towards the funnel's end, managing to hold onto it. Here is where his strength and monkey-like acrobatics turned out useless, as his shoes would slip as he tried to climb up, while his hands would slowly slip away due to tiredness. This resulted in him falling from a great height, right into a pile of boxes. As soon as he crawled out of the remnants, two of the thugs grab him and slam him against the superstructure's wall; he then asks Clayton for help but Clayton reveals to him that he'll attack the gorilla's nest. Tarzan is locked up in the ship, desperately trying to get out, at one point even shows aggression toward Jane when she tries to calm him down and realizes that Kerchak was right about him betraying his family. Ultimately, he is rescued by Terk and Tantor after they heard Tarzan's cry.
After being rescued, he returns to wear his usual clothes, rescues the gorilla pack and defeats Clayton's men, with the help of some more animals he summoned to help him in the rescue; including Terk and Tantor and Jane and her father. After the rescue, Clayton shoots Tarzan in his arm. When Kerchak sees this, he tries to intervene but is unfortunately, shot by Clayton. In a fit of rage, Tarzan aggressively attacks him, but is forced back by Clayton's shots. Realizing he doesn't have the advantage over Clayton, he moves up to the trees, which lures Clayton to follow him.
On the tree branches, Tarzan and Clayton engage in a struggle in which the two are evenly matched. He manages to kick Clayton off and goes after his rifle. He aims it at the ruthless poacher with Clayton taunting him to be a man and shoot him. Realizing that killing him would make him no better than Clayton, Tarzan fools him with a gunshot imitation and then smashes the rifle to pieces on a tree branch declaring that he is not a man like him. Infuriated, Clayton pulls out a machete and furiously tries to kill him. Tarzan manages to escape with the aid of nearby vines, but quickly meets a dead end. Clayton manages to catch up and continues to hack and slash at Tarzan, but to no avail.
Using the vines, Tarzan ensnares Clayton in them and seemingly brings the fight to a stand still. Refusing to lose to the ape man, Clayton aggressively rips them with his teeth and machete, unaware that one of them is hanging into his neck while the vine he is hanging on is weakening, just waiting to snap. Tarzan realizes this and tries to warn him, but Clayton continues to the cut vines around and eventually cuts the one he was hanging on to, causing both him and Tarzan to fall. Clayton unfortunately meets his end when the vine around him snaps his neck while Tarzan lands to the ground as lightning illuminates the jungle, allowing him to witness the corpse of his enemy.
Tarzan moves toward a near-death Kerchak, whom telling him that he'll now lead the pack. Kerchak also tells him that he was wrong about him and that Tarzan has been a member of the pack all along. Kerchak, having finally accepted Tarzan as his son, then dies in the scene of heavy rain and the sadness of Jane, her father, Tarzan, and the gorillas. Tarzan pounds his chest, indicates his leading to the gorillas.
The next day, after his arm has been treated and bandaged from the almost fatal gunshot, Tarzan stands on the beach, watching sadly as Jane and her father leave him. One of her gloves fly towards him, which only made him more depressed. After Jane realizes that she loves him, she jumps off the boat and runs toward him, much to his surprise and the two finally share a kiss. Later, Jane's father joins his daughter, telling the captain to tell everyone back in England that he never found them; "After all, people get lost in the jungle everyday," he says. Finally, Tarzan is seen swinging with his wife, Jane, to a tree with his big family (including Jane's father, Kala, and Terk with Tantor as a little help) as the King of The Jungle.