According to a report by Variety, the accident was a result of a car stunt gone wrong, which left the "Teen Wolf" actor with multiple broken bones.
The 24-year-old actor, who is also popular for his role in MTV’s "Teen Wolf," was hit by a car while filming a stunt scene in Vancouver, Canada.
According to a statement released by 2Oth Century Fox, O'Brien was immediately transferred to a local hospital for observation and treatment.
Production on the film has also been shut down while the actor who sustained multiple injuries, recovers.
"Maze Runner: The Death Cure" is directed by Wes Ball who directed the past two, from a screenplay by T.S. Nowlin adapting the YA novels of James Dashner.
In the upcoming sequel, young hero, Thomas, embarks on a mission to find a cure to a deadly disease known as the "Flare". "The Death Cure" stars the injured star alongside Thomas Brodie-Sangster, Rosa Salazar, Ki Hong Lee and Dexter Darden.
The 2014 original grossed $102 million, with its 2015 follow-up "The Scorch Trials" grossing $82 million domestically.
The last major injury on set was in 2014, when Harrison Ford broke his leg while shooting "Star Wars: The Force Awakens."
The film is currently slated for a February 17, 2017 release date.
Watch "The Scorch Trials" clip below.