Kovu is a stocky lion cub with red-brown fur. He has a hair tuft of dark brown fur, the beginnings of a mane, on the top of his head. On either side, fur sticks out from his chin. His forelegs have tufts of dark brown fur emerging from them. His eyes are green, with dark rims resembling to Scars. His paws, underbelly, and muzzle are a beige color, and his underbelly doesn't extend up over his neck. He has an outlander shaped, black nose and three whiskers on either side of his muzzle.
As seen in a painting as a teenager, not much about Kovu changes except that he has grown bigger and his mane has grown bigger.
In Return to the Pride Lands, Kovu has become a young adult with a full mane and has a scar on his eye, identical to his adoptive father, and former predecessor Scar. His jaw is quite small, and his muzzle color is present at the tip of his snout. His inner ears have changed color, becoming dark pink, and he now has four whiskers on each side of his muzzle.
Kovu, unlike his mother and siblings, is very relaxed, kind and friendly, and doesn't necessarily believe in their cruel and violent, evil ways. Despite this, when his mother asks him to do something, he will obey and even approach his older sibling, should he try to disobey her. He holds no animosity towards the Lion Guard, frequently avoiding confrontation with them. He is shown to be excited at the prospect of living in the Pride Lands so he could see Kiara again.
Years later, it's revealed that Kovu was manipulated by Zira into believing Simba was the enemy, which implies that he was at one point cruel and murderous, but this later changes when he befriends Simba and reconnects with his daughter, Kiara. His initial refusal to fight, a trait he had as a cub, is resurrected when he attempts to stop an attack on the Pride Lands held by Zira. He is willing to put the past behind him, as when he sees Kion again, he does not hold any animosity towards him for their past meeting and he later befriends him as his brother-in-law.
Kovu originally lived in the Pride Lands with his mother and siblings during the reign of Scar, who picked Kovu to be his heir. Sometime after this, Scar's nephew, Simba returned to the Pride Lands and battled Scar. He defeated him and afterward banished Kovu, his family and several other lionesses loyal to Scar to the Outlands.
Sometime after this, Kovu met and briefly befriended Simba's daughter Kiara, after they worked together to escape crocodiles.
A while later, Kovu came across Nuka, who was pinned down by Kion, Kiara's younger brother, who had come to the Outlands to solve the problem of lions not sharing a waterhole with his hyena friend Jasiri's clan. The two brothers, along with Kion and Jasiri circle each other with Kion questioning the two on why they are in the Outlands and not the Pride Lands, to which Nuka says they are not welcome there. After learning that Kion is Simba's son, Kovu wondered if the King would let his family back into the Pride Lands, with the possibility that he could see Kiara again. Kion is surprised to hear that Kovu knows his sister, to which Kovu says it was a while ago, before telling Nuka that they should take Kion and Jasiri to see Zira. He agrees with a sinister tone to his voice, and he and Kovu lead Kion back to their mother, Zira.
Kovu excitedly informs his mother their visitor is Simba's son Kion and waits to see what his mother has to say on the matter. When the conversation turns to Kion's ability as a leader of the Lion Guard, Kovu's curiosity is piqued when Zira starts to reveal her knowledge on the Roar of the Elders. He is shocked when Kion can conjure water from using his Roar on a nearby cloud. Eventually, his mother drags Kion away from everyone to speak with him in private, leaving him alone with his sister Vitani, Nuka and Jasiri with an order to play nice.
Later, Nuka becomes antsy over his mother's absence and attempts to strike Jasiri. Kovu leaps between them, urging him not to start anything as per their mother's words. Jasiri laughs at him, assuring him that she can play any game Nuka wants too much better than he can. Just as Nuka pounces, Zira returns, much to Kovu's delight. Kovu then watches his mother force Jasiri out, claiming that Kion has sided with the lions. Zira then leads her children back to Kion.
Kovu becomes confused when he sees that Kion has been cornered, and asks his mother why they can't be friends. His mother tells him that Kion made the choice to side with the hyenas and that it is his fault. When Nuka voices his concern over the Roar, Zira explains that Kion cannot use it against them since using it on lions was how Scar lost it all those years ago. Zira then offers Kion one final chance to side with her, but Kion notices Ono flying overhead and calls the Lion Guard together. Kovu becomes fearful and immediately withdraws himself.
When the Outsiders gather together again, Zira tells them to stand tall. Kovu is noticeably upset about the situation and lowers his head. Kion is then reminded by Bunga that Scar lost the Roar by using it for evil and not for using it against lions, and, despite Zira's pleas to listen to her, Kion unleashes the Roar on them. Kovu quickly dives out of the way and shields himself, missing the impact entirely. When the Outsiders vanish over the canyon, Kovu looks toward Kion, who glowers at him. When he moves a step towards him Kovu runs after his family, calling for his mother to wait for him.
Sometime after Zira died, Anga spots Kovu standing on top of Pride Rock. When Vitani and her Lion Guard see Kion's Guard, they start to fight, but Kiara and Kovu come to break it up. Kiara explains that the Outsiders have joined Simba's pride. Vitani, not noticing that it's Kion, says that it's been a long time since she's seen him. Kovu asks what's going on. Bunga asks the same question. Kion returns to Pride Rock and his family. They all explain to him and the rest of the Guard what happened to Zira. Simba then announces that Kiara and Kovu will be the future King and Queen of the Pride Lands.
Along with the rest of the royal family and other Pride Landers, Kovu watches as Kion becomes King of the Tree of Life and mate of Queen Rani.