The pictures of Mickey's wife in the movie are pictures of Michael Biehn's real life wife Jennifer Blanc-Biehn.

The film was shot in chronological sequence.

Mickey was more of a racist in the original script.

The cast did a lot of improvisation throughout the shooting of the movie.

The opening pre-credits scenes were shot in a single day.

The haircutting scenes were done in a single take.

The production hired a nutritionist who started the actors on a diet plan.

Melissa George, Seann William Scott, Robert Patrick and Raphaël Personnaz were originally going to star in this project.

Shooting was delayed in part by the eruption of Iceland's Eyjafjallajökull volcano, which paralyzed air travel between Europe and North America.

Michael Eklund improvised the moment where he defecates in front of Mickey, and when he imitates his magic trick with Mickey's own finger.

Michael Eklund is the one who suggested that his character should wear Marilyn's night gown in the final act of the movie.

Milo Ventimiglia was originally supposed to be cast as Adrien, but Ventimiglia wished to play a more antagonistic character to differ from his previous roles, and was then cast as Josh.

The movie was initially titled "The Shelter", but was later changed to "The Fallout". Due to the similarity with the video game Fallout 3 (2008), the title was finally changed to "The Divide".

According to Xavier Gens, Eva was not supposed to fight with Josh or yell at him during Mickey's torture scene. Gens claims that Lauren German was not yelling at Josh but rather at Milo Ventimiglia himself, since Ventimiglia had been screaming and yelling at the other actors all day in order to prepare the scene.

Milo Ventimiglia believed that his performance as the psychotic Josh was so disturbing that he forbade his mother to see it. She did, and later questioned Ventimiglia if he had a traumatic experience when he was younger that she didn't know about, worried that her son's mental state influenced his performance.