Kerchak lived in the African jungle with his mate, Kala, their young son, niece Terk and the rest of their troop, which Kerchak led. Kerchak was a loving and warm father to his son.
One night while Kerchak and Kala were asleep, their son saw a frog and chased after it. However, the youngster ends up running into a leopard named Sabor, who chases after him. Kerchak and Kala hear what is going and race to their son's aid only to arrive and see him being eaten alive by Sabor. A devastated Kerchak and Kala mourn their son's death.
Afterwards, Kerchak changed from being loving and warm to strict and stern. Kerchak moves the troop to another part of the jungle, most likely to prevent any of the troop's other youngsters from being is danger. Unbeknownst to the troop, Kala leaves after hearing crying. Later that day, Terk notices Kala returning, which alerts the others. A relieved Kerchak goes to Kala and sees Terk holding a human baby boy. Upon seeing Kerchak, Terk hands the baby to Kala and tells Kerchak that Kala is going to be the baby's new mother. Kala tells Kerchak that she rescued the baby from Sabor. Kerchak tells Kala that the baby will not replace the one they lost and tells her to take the boy back, saying that he cannot let Kala endanger their family, to which Kala holds the baby out asking if he looks dangerous to Kerchak,
causing Kerchak to roar in anger. Kerchak calms down and asks Kala if the baby was alone, to which Kala replies that Sabor had killed his parents and that there are no others. Kerchak reluctantly agrees to allow Kala to keep the baby but tells here that it does not make the baby his son. That night, as the troop go to bed, Kerchak looks over at Kala and the baby, whom Kala has named Tarzan and gives Kala a dismayed look.
A few years later, Tarzan (now a young boy) runs into Kerchak, but is able to be led away by Terk. Later that day, an herd of elephants stampede through the jungle where the troop are eating from termite mounts. Kerchak rescues one of troops infants from the stampede and takes it to it's mother. He then goes to the river's edge where Tarzan claims to be resonsible for causing the stampede. Kerchak scolds Tarzan as he could have killed someone. Kala then comes to Tarzan's defence and calls out Kerchak for not giving Tarzan a chance to prove himself, to which Kerchak replies that Tarzan will never be one of them.
Kerchak is then seen during a montage of Tarzan continuing to trying to fit with the group as he grows up.
When Tarzan becomes a young adult, Kerchak watches in annoyance as he and Terk play fight. Just then, Sabor arrives and attacks the troop. Kerchak battles Sabor, who manages to get the upper hand. Fortunately, Tarzan comes to Kerchak's defence and battles and kills Sabor. Tarzan then presents Sabor's corpse to Kerchak and earns the silverback's reluctant respect. Suddenly a gunshot is heard, resulting in the troop leaving sans Tarzan, who goes to investigate the noise. Later that day, Kerchak along with Kala and some of the troop hear music and go to investigate and find Tarzan, Terk, Tantor and several of the troop's younger members playing in a human camp. Upon seeing a human woman named Jane Porter, Kerchak orders the troop to leave the camp. Kerchak later tells the troop to keep away from the humans, much to the annoyance of Tarzan. Kerchak tells Tarzan to protect the family and stay away from the humans.
Wanting Jane, her father Archimedes and their guide Clayton to see his troop, Tarzan has Terk and Tantor disguise themselves as Jane and her father in order to keep Kerchak away. However, the pair accidentally bring Kerchak back to the troop. Kerchak is shocked to see the humans and attacks Clayton after seeing him point his rifle at a young gorilla. Tarzan restrains Kerchak and tells the humans to leave. Tarzan lets go of Kerchak and says that he is sorry. Kerchak tells Tarzan that he told him to protect the family, instead he has betrayed them.
Clayton later turns against the Porters and Tarzan and imprisons them, before he and his men attack the gorillas and begins to put them in cages to sell them on the black market. Kerchak attempts to protect his troop, only to be restrained. Clayton, remembering Kerchak, declares that he would be better off stuffed. Just then, Tarzan, the Porters, Terk and Tantor arrive and Clayton and his men and free the gorillas. When Clayton threatens Tarzan, Kerchak comes to his defence, only to be fatally shot in the chest by Clayton.
After Clayton's death, Tarzan returns to the troop and sees Kala tending to Kerchak. Tarzan asks for Kerchak's forgiveness, to which Kerchak replies that Tarzan should forgive him for not knowing that he was one of them all along. In his dying breath, Kerchak makes Tarzan the new leader of the troop and accepts him as his son.
"I said he can stay. That doesn’t make him my son"
"You almost KILLED someone!"
"(mimicking Kala) He’s only a child. (rudely) THAT’S no excuse, Kala, you can't keep defending him.
"You came back."
"No, forgive me for not understanding that you have always been one of us. Our family will look to you now."
In the original novel, Kerchak was a major antagonist. This role however is given to Cecil Clayton in the film, with Kerchak becoming the false antagonist instead.
Kerchak is not bad or an antagonist, since he only wants to protect the gorillas and his adoptive son Tarzan from danger, just because he wants Tarzan to protect his family from Clayton (but later except Jane and her father), so he was still neutral first at the beginning.
He was stopped by Tarzan from attacking Jane and her father. This doesn’t mean he was bad, he was just neutral first because he was over-protective to Tarzan.
It is possible that besides his and Kala's son, Kerchak have been the father of Terk, Flynt, Mungo and the other young gorillas in the troop as he is the only mature adult male in the troop and that in real life, only the silverback male of a gorilla troop can mate with the females. Though there have been cases of silverbacks allowing other males to mate with the females. This could be the case for the film as Terk and the other young gorillas do not refer to Kerchak as Dad or Father.