Brian O'Conner is one of the three lead protagonists of the series. He appears in all of the films in the series except for Tokyo Drift which he only shows up in one scene passing the RX-7 before the speed trap in his blue GT-R. During the events of the first film, Brian O'Conner is working as an undercover detective with the LAPD on a joint the FBI, who assigns him the task of solving a series of semi-trailer truck hijackings around L.A. While investigating the street race scene, he meets Dominic Toretto and infiltrates his crew while getting involved in a relationship with Toretto's sister, Mia. He allows Toretto to escape arrest at the end of the first film and leaves Los Angeles after to avoid his own arrest. In the second film, he is shown living in Miami as a street racer, and after winning a race, O'Conner is caught by U.S. Customs agents and offered a deal to take part in a joint Customs/FBI operation in exchange for his criminal record being wiped clean. He teams up with childhood friend Roman Pearce, and the two go undercover as street racers, eventually apprehending the ruthless drug lord, Carter Verone.

In the fourth film, after having his crimes pardoned, O'Conner becomes an FBI agent and is given the task of bringing down Arturo Braga, a known drug trafficker. O'Conner, as well as Toretto, both infiltrate Braga's crew. While Braga is eventually apprehended, Toretto is arrested and sentenced to prison as well, resulting in O'Conner, Mia, and members of Toretto's crew intercepting the prison bus to free Dominic from custody. In Fast Five, O'Conner and Toretto get caught in a crossfire with corrupt businessman and ruthless drug lord Hernan Reyes in Rio de Janeiro and plot to steal all of Reyes' money to buy their freedom. It is revealed in Fast Five that O'Conner's father was not there for him and O'Conner does not know anything about him, unlike the close bond that Toretto's father had with both his children. He is often worried that he will behave in the manner that his father did, but Toretto reassured him that he won't because he will keep an eye on him if he does. O'Conner had been in juvenile detention with Roman before he became a cop. O'Conner has also rekindled his relationship with Mia, and she becomes pregnant with his child. In the sixth film, O'Conner, Toretto, and Mia live peacefully in the Canary Islands in Spain, where Mia gives birth to their son. O'Conner joins Toretto's team in complying with the request of Agent Hobbs to take down rival gang leader Owen Shaw. When the team realizes that Braga worked for Shaw, O'Conner volunteers to enter the United States to interrogate him about Shaw. After successfully questioning Braga and returning to London, O'Conner starts to feel guilty for letting Letty go undercover, which led to her amnesia and subsequent work for Shaw. The group captures Shaw and convinces Letty to side with them. O'Conner apologizes to Letty, who says that she might not remember him, but if she did work for him, she would have done of her own free will. Shaw reveals that he had captured Mia, leading to a high-speed chase after Shaw's airplane, where Mia is rescued and Shaw is killed. Hobbs then grants the group's amnesty, and the entire crew move back to America, where Mia, Toretto and O'Conner have decided to reside in the old Toretto home.

O'Conner was first unknown with the car tuning (although he owned a Mitsubishi Eclipse tuned in the first film), but with meeting Toretto, he became more positive, active in racing scene, becoming a skilled mechanic. He is very interested in tuners, especially Nissan Skyline models. He owned two Nissan Skyline GT-R R34's (one in the second movie and one in the fourth), Nissan C10 Skyline and finally a Nissan GT-R. O'Conner is portrayed by late actor Paul Walker.