12-year-old Dre Parker (Jaden Smith) and his mother, Sherry (Taraji P. Henson), arrive in Beijing from West Detroit, looking to build a new life. As Dre adapts to this unfamiliar environment, he develops a crush on a talented young violinist named Mei Ying, but their budding romance faces obstacles from Cheng (Zhenwei Wang), a kung fu prodigy and Mei's family's associate, who resorts to violence to keep them apart.
One day, as Cheng and his friends viciously attack Dre, he is unexpectedly rescued by the enigmatic Mr. Han (Jackie Chan), the building's maintenance man. Han reveals his skills as a kung fu master, effortlessly dispatching Dre's attackers. After Han helps Dre recover from his injuries using traditional fire cupping techniques, they approach Cheng's teacher, Master Li, in hopes of brokering peace. However, Master Li, who teaches a brutal philosophy of combat with no mercy, challenges Dre to fight Cheng. Han reluctantly agrees, setting the stage for a showdown at an upcoming tournament, while insisting that Dre stay clear of Cheng's harassment until then.
In preparation for the tournament, Han begins to train Dre, but the young boy is puzzled by Han's unconventional methods, which initially involve repetitive tasks like putting on and taking off his jacket. Frustrated, Dre is ready to give up, only to discover that these simple movements serve to teach him critical defensive techniques that he can later apply during real attacks. Han emphasizes that true martial arts mastery relies on calmness and maturity, rather than sheer strength.
While their friendship blossoms, Dre convinces Mei Ying to cut school for a fun day together. However, when Mei Ying's parents forbid her from seeing Dre, her commitment to her upcoming violin recital causes a rift between them. During a touching moment, Dre encourages Han to confront his own past trauma as the anniversary of his wife and son’s deaths approaches. Together, they help each other heal – Dre doing so by writing an apology note to Mei Ying's father, who eventually permits her to support Dre at the tournament.
As the tournament unfolds, Dre faces numerous skilled opponents, finding his footing as he progresses to the semifinals where he encounters the vicious Liang, another one of Cheng’s allies. Under Master Li’s ruthless command, Liang is instructed to break Dre’s leg in the match. Despite being injured and facing overwhelming odds, Dre, fueled by Han’s teachings, bravely returns to the arena. Employing the one-legged stance he observed from a woman in the mountains, Dre invokes the reflection technique to outsmart Cheng in a gripping final showdown. With impressive agility, he ultimately flips the tables, landing a decisive kick and overcoming the challenges before him, earning the respect of both Cheng and his peers, as well as solidifying his bond with Mr. Han.
