Hua Mulan is an adventurous and lively girl in Imperial China, much to the dismay of her parents Zhou and Li, who hoped that she would marry a good spouse one day. Mulan is arranged to meet with a matchmaker as a young woman in order to demonstrate her suitability as a future wife. Flustered, Mulan tries to pour tea in front of the matchmaker, but a spider terrifies the latter’s younger sister Xiu, causing an accident that ruins the teapot, prompting the matchmaker to label her a disgrace in front of her family.
An imperial garrison in the north is attacked by Rouran troops led by Böri Khan. They are helped by Xianniang, a witch who uses her magic to impersonate a surviving soldier and report the attack to the Emperor of China, who then passes a conscription decree requiring every family to send one man to fight Khan’s soldiers.
Imperial soldiers arrive in Mulan’s hamlet to enroll recruits, and because he has no sons, Zhou is obliged to commit his duty, falling over in front of the soldiers owing to his damaged leg. Mulan departs with his armor, horse, and sword to take her father’s place, realizing that he has no hope of surviving. Mulan arrives at Commander Tung’s training camp, which is administered by an old friend of Zhou’s. She eventually becomes a skilled soldier under his instruction, alongside dozens of other inexperienced recruits, without revealing her true origins.
As the Khan’s army advances, Tung is forced to stop training and put his regiment into battle. Mulan goes off on her own to pursue some troops, but she is met by Xianniang, who mocks her for pretending to be a man. She tries to kill Mulan, but her strikes are thwarted by the leather Mulan had bound around her chest to conceal her identity. Mulan takes off her male disguise and returns to the combat just as the Rourans launch a trebuchet attack on her fellow soldiers. Mulan manipulates the trebuchet into firing on a snowy mountain, producing an avalanche that burys the Rourans, using discarded helmets and her archery skills.
Mulan returns to camp and saves Chen Honghui, a soldier she had befriended there. She gets ejected from the army and begins her journey home, unable to conceal her true gender any longer. On her route, she meets Xianniang, who explains that she, too, was rejected by her people and fights for Böri Khan only because no one else does. She also discloses that Khan’s attacks on the outposts were merely a distraction from his ultimate aim, which is to capture and assassinate the Emperor for assassinating his father. Mulan returns to her regiment, risking execution, to warn them of the approaching capture. Tung chooses to believe her and enables her to lead a unit to the Emperor’s palace after the troops she met stand up for her.
Xianniang impersonates the Imperial Chancellor with her sorcery and persuades the Emperor to accept Böri Khan’s challenge to single combat, while the city guards are removed from their posts. The guards are assassinated, and the Rourans prepare to execute the Emperor by burning him alive. Mulan’s squad diverts the Rourans’ attention away from Mulan’s mission to save the Emperor. Khan tries to snipe Mulan with an arrow, but Xianniang changes into a hawk and sacrifices herself by intercepting the projectile. Mulan kills Khan after disarming her and destroying her father’s sword. She sets the Emperor free, and he invites her to join his personal guard. She passes down the offer and returns to her hometown.
Mulan is reunited with her family for the first time. Mulan is presented with a new sword by a delegation from the Emperor, led by Commander Tung, who also makes a personal request that she join the Imperial Army as an officer.