Simba's birth somewhat caused resentment in Scar, who knew very well that his nephew will replace him as heir to the throne. When he was a cub, his father taught him about responsibilities of being a king and the Circle of Life. Once, Scar tricked him and his best friend Nala into exploring a forbidden elephant graveyard, despite the protests of Mufasa's hornbill majordomo Zazu. At the graveyard, three spotted hyenas named Shenzi, Banzai and Ed attack the cubs before Mufasa, alerted by Zazu, rescues them and forgives Simba for his actions. That night, the hyenas, who are allied with Scar, plot with him to kill Mufasa and Simba (at that time, Scar had made deals with the Devils).
The next day, Scar lures Simba to a gorge and tells him to wait there while he gets Mufasa. On Scar's orders, the hyenas stampede a large herd of wildebeest into the gorge. Mufasa rescues Simba, but as Mufasa tries to climb up the gorge's walls, Scar throws him back into the stampede, where he is trampled to death. After Simba finds Mufasa's body, Scar convinces him he was responsible for his father's death and advises Simba to flee the kingdom. As Simba leaves, Scar orders Shenzi, Banzai and Ed to kill the cub, but Simba escapes. That night, Scar announces to the pride that both Mufasa and Simba were killed in the stampede and steps forward as the new king, allowing a pack of hyenas to live in the Pride Lands.
The High Council, having seen what happened to Simba, brought his father to Olympus where they made him the god of rain. Then, they influenced events to lure Timon and Pumbaa into caring for the lion cub in the jungle. When he grew up, he saved the duo from a lioness who is his old friend, Nala. She convinces him to return to the Pride Lands since it has no food and water. Simba refuses, feeling guilty over his father's death. He then meets Rafiki, who takes him to meet Mufasa as a spirit. After being told that he must take his rightful place as king, Simba gains enough courage to face his past and defeat Scar. He brings Nala, Timon and Pumbaa with him to the Pride Lands.
At the Pride Lands, Simba confronts Scar over his father's death. Scar mocks him and soon enough, after he admitted that he killed Mufasa, he and Simba fought for control of the Pride Lands. Scar begs Simba for mercy, saying he is family and placing the blame on the hyenas. Simba says he does not believe Scar anymore but spares his life and commands him to forever leave the Pride Lands. Scar meekly walks past him, but then attacks his nephew. After a fierce fight, Simba throws his uncle off Pride Rock. Scar survives the fall, but is attacked and eaten alive by the hyenas, who overheard his attempt to betray them. At this point, Simba regains his kingship over the Pride Lands.
He was reluctant of his daughter Kiara being in love with Kovu, but ever since the battle between the Outlanders and the lions of the Pride Lands, he realizes that the pride must unite together and approves of Kiara and Kovu's marriage.
He currently serves as current king of the Pride Lands and an ambassador of cat-kind with Bagheera and Rajah.