In 1964, after the passing of his beloved wife, Ip Man (Donnie Yen), a modest yet skilled Chinese Wing Chun master from Foshan, learns that he is suffering from throat cancer, a consequence of his smoking habits. His rebellious son, Ip Ching (Jim Liu), faces expulsion for standing up against a bully, prompting Ip to accept an invitation from his former student Bruce Lee (played by Danny Chan) to travel to San Francisco. This trip also serves as an opportunity for Ip to seek a suitable school for his son.
In San Francisco, Bruce Lee has caused a stir within the local martial arts scene by establishing his own Wing Chun school, where he not only trains Americans but also publishes an English book on martial arts. However, Ip soon realizes that to enroll his son in a new school, he requires a referral letter from the Chinese Consolidated Benevolent Association. The association's president, Wan (Wu Yue), refuses to provide the letter, insisting that Ip agrees with the grandmasters' stance against Bruce’s teachings, particularly his acceptance of non-Chinese students and the publication of his English book.
A confrontation ensues between Ip and Wan, where they engage in a brief combat to test their martial skills, leading Ip to leave empty-handed. Shortly after, while departing from a meeting with the school principal, Ip encounters Yonah (Vanda Margraf), Wan's daughter, who is being bullied by Becky (Grace Englert). Ip intervenes, ensuring Yonah's safety, inadvertently causing Becky to injure herself in the process. Infuriated, Wan believes that Ip is using his daughter to obtain the referral letter and challenges him to a duel, which is interrupted by an earthquake. Ip, asserting that his intentions were solely for Yonah's safety, declines the challenge, much to Wan's dismay.
Meanwhile, Becky's father, Andrew Walters (played by Andrew Lane), who works with the Immigration and Naturalization Service, feels pressured to hold the Association accountable and deport its Chinese members. In parallel, Hartman (Vanness Wu), a Staff Sergeant in the U.S. Marines, suggests incorporating Chinese martial arts into their training. Despite demonstrating the superiority of their current Karate methods through a fight between Barton Geddes (Scott Adkins) and the Marines' Karate instructor, Hartman gains approval from his superior officers to film the Mid Autumn Festival at the Association for further study, much to Geddes' annoyance.
The festival takes a tumultuous turn when Geddes challenges the grandmasters, defeating several before Ip intervenes, besting Geddes in a fierce battle. Complications arise when Wan is detained by immigration officers, and upon witnessing Frater's defeat, Geddes storms the Association to locate Wan. After a series of encounters, he resort to threats against Walters to secure Wan's release into Marine custody, leading to a confrontation between Geddes and Ip at the camp.
After a grueling fight, Geddes is defeated by Ip. Despite Wan preparing the sought-after letter for Ip, he reveals his reluctance to move to San Francisco, as he finds the city unappealing. In a touching moment, Ip reconciles with his son and instructs him to film a demonstration of Wing Chun on the wooden dummy.
By 1972, as Ip succumbs to his illness at age 79, Bruce Lee honors his master at the funeral. The story concludes with the revelation that in 2001, the Marines officially incorporated Chinese martial arts into their training routines, a lasting testament to Ip Man's legacy.
