The film starts with the presentation of Simba and Nala's new cub, Kiara, which to Timon and Pumbaa's surprise is a girl. As she grows into a cub, Simba is over protective of her and wants her to stay in sight of Pride Rock at all times. He also warns her to stay away from the Outlands. Kiara's confused why, but Simba says she'll understand someday and sends her off to play. He gets worried and sends Timon and Pumbaa to watch her.
Kiara is chasing a butterfly and tries to catch it. After it flies off she sits on a rock and sees the Outlands. She thinks it's cool and wonders what's there. Timon and Pumbaa sneak up from behind and startle her. Kiara falls into the water and Pumbaa jumps in after her.
Once Kiara's out of the water, Timon checks her over to see if she's hurt. Kiara is annoyed by the treatment they're giving her. Kiara asks them to listen to her. Timon replies "I'm sorry, I wasn't listening. Did you say something, princess?"
Kiara protests, "I'm not just a princess you know! That's only half of who I am!"
Pumbaa asks who her other half is, but Kiara doesn't know. Timon suggests they eat and gets some grubs. While he and Pumbaa argue whether slimy or crunchy is better, Kiara runs off.
She falls off a log and bumps into a hostile cub: An Outsider. The Outsider says he doesn't need anybody and can take care of himself while walking onto some rocks. Kiara is impressed and follows him.
It turns out that they were stepping on crocodiles not rocks and they attack. They manage to make it back to land, and are being watched by the Outsider's mother: Zira. It turns out the Outsider's name is Kovu. Kiara tries to play tag with him, but he doesn't understand, so she tries play fighting.
Simba interrupts by roaring, soon followed by Zira. Simba tells her to get out, but Zira insists it's Scar's land and introduces him to Kovu: who was chosen as Scar to become king. Simab tells them to get out and leaves with Kiara.
Simba scolds Kiara and then tells her she's part of him and The Great Circle of Life. He teaches her an important lesson "We are One" and tells her she'll understand someday.
In the Outlands, Nuka cuts a branch that his sister Vitani was chewing and asks where Kovu is. Vitani is mad since he was supposed to be watching him. Nuka protests and says he should be king instead and that he could be a leader if Zira gave him a chance.
He tries to impress her, but she yells at him for not watching Kovu. Kovu says it wasn't Nuka's fault and that he went off on his own. Zira scolds him and scoffs at the idea of Kovu and Kiara being friends. Then she realises he can get close to Kiara to Simba.
Many months pass and Rafiki is painting on his tree and commenting to Mufasa's spirit how Kiara is growing into a beautiful queen, but Kovu is growing with hate. Mufasa's spirit shows him they need to be together to unite their feuding prides.
Kiara is now a grown up and ready for her first hunt. Simba promises to let her do it on her own, but sends Timon and Pumbaa to watch over her. Kiara is having trouble hunting and soon finds out that Timon and Pumbaa are following her and runs off.
Nuka and Vitani start a fire in the grasslands. Zira and Kovu are watching and Zira ends Kovu to "save" her. Kiara is mad that he brought her back to the Pride Lands. Kiara changes her attitude when she finds out it's Kovu.
Kovu asks Simba to join the Pride, but he refuses. He decides to reserve judgment and they go back to the Pride Lands. Kovu tries to go into the cave, but Simba doesn't let him and he's forced to sleep outside.
Kiara thanks him for saving her and he comments on her poor hunting skills. They make a deal for Kovu to teach her to hunt.
Nuka and Zira are watching from the base of Pride Rock and Nuka is furious that he didn't attack Kiara. Zira hushes him and says the plan's working perfectly.
That night Simba has a dream about the stampede, but with Kovu in place of Scar.
The next day Kovu is getting ready to attack Simba, but Kiara tells him she's ready for his lesson. He has her try pouncing, but he manages to dodge her since he's loud. He tries to show her how it's done and tries to get a bird. He ends up catching Timon who begs for his life.
Kiara is mad thinking her father sent them, but it turns out Timon and Pumbaa are just there for the bugs. However there are birds eating all of them and they are unable to scare them off. They get Kovu and Kiara to roar to scare off the birds and end up chasing them. They run into some rhinos that chase them before they manage to find a hiding spot. As Timon and Pumbaa start getting out, which pushes Kovu and Kiara closer causing them to kiss.
Some time has passed and Kovu and Kiara are making constellations with the stars. Kovu admits he's never done it before. Kiara is surprised and tells him about The Great Kings of the past. Kovu asks if she thinks Scar's up there and they both become uncomfortable. Kiara nuzzles him to calm him down.
Simba, who was watching them, starts talking to his father's spirit about Kovu. Nala enters and tells Simba to give Kovu a chance.
Kovu starts feeling guilty and starts to leave, but is stopped by Rafiki. He teaches them about Upendi, which means love. When Kovu and Kiara get back to Pride Rock Simba notices how close they've gotten and invites Kovu inside the den.
Vitani is watching them and cheers for Kovu to herself. She is outraged that he doesn't attack and runs off to tell Zira.
The next morning, Kovu plans to tell Kiara he was sent by Zira to kill Simba, but he doesn't want to do it because he loves her. He tries to tell Kiara, but Simba says he wants to talk to Kovu and they go out.
He tells Kovu the story of Scar from his perspective and takes him to where the fire was. He bats up some dust revealing a sprout.
Zira and the Outsiders surround them and Zira says Kovu planned it. Simba is mad and tries to fight off the Outsiders. Nuka chases him up a dam, but some of the logs fall and crush Nuka.
Zira digs out Nuka and then he dies.
Simba limps back, half alive, and tells Kiara, Timon and Pumbaa that it was Kovu's fault. Kiara doesn't believe it.
Zira meanwhile blames Kovu for Nuka's death and claws his eye, giving him a scar like Scars'. Kovu says he wants nothing more to do with Scar and runs off. Zira tells the Outsiders that it's time to attack.
Kovu goes back to the Pride Lands asking for forgiveness, but gets exiled. Kiara tries to reason with her father, but he won't listen and tells her she cannot leave with an escort. Kiara runs into Pride Rock crying and then notices the rocks are crumbling. She breaks through and looks for Kovu.
She gives up hope after a while, but Kovu finds her and they reunite happily. They look at their reflection in the water and their face has become one. Kovu muses "Hey look, we are one."
Kiara remembers what her father told her and says they need to go back.
Meanwhile the Outsiders start an attack on the Pride Lands, which is interrupted by Kovu and Kiara jumping between Simba and Zira.
Kiara reminds all the lions they are one, and they join the Pride Land side. Except Zira, who tries to attack Simba, but Kiara jumps in the way.
Zira is dangling off the ledge and refuses Kiara's paw. She slips and falls into the water, dying.
Simba accepts Kovu and the Outsiders into the Pride. Then Kovu, Kiara, Simba and Nala go to the tip of Pride Rock and roar.
Mufasa has the last words "Well done, my son. We are One."