Nicholas Hoult told reporters how he and Jude Law, adversaries in the film, did not speak or interact with each other for the first four weeks of filming in an attempt to distance themselves from each other.
Jude Law's FBI agent Terry Husk is a composite of the many law enforcement officials who participated in the investigation, a fictional character with whom the filmmakers could paint a portrait that would dramatically contrast with the real-life Bob Mathews.
Director Justin Kurzel tasked Nicholas Hoult with following Jude Law around Calgary for a day without his fellow actor knowing.
The character of Tony Torres (played by actor Matias Lucas) was based on Thomas Martinez, a former member of The Order who would later turn government informant against the gang. He would later author a book about his experiences in The Order titled Brotherhood of Murder with John Guinther. His book was also the inspiration for a TV movie eponymous with his book with William Baldwin playing Martinez and with Peter Gallagher playing the gang leader Robert Jay Mathews. Martinez (while in hiding) now gives speeches and lectures about the threat that domestic extremist organizations pose to the United States.
Nicholas Hoult joined the production the day after he had completed filming his scenes for Nosferatu (2024). The day he finished filming on The Order (2024), he joined Clint Eastwood for Giurato numero 2 (2024).