In an interview, Alex Wolff explains that he wanted to actually break his own nose for the scene where his character slams his head into a desk. Director Ari Aster respectfully declined that offer and told Wolff they'd give him a soft, cushioned desk for the scene. When it was time for the scene to be shot, Wolff slams his head into the desk only to discover that it was not soft nor made out of foam that resulted into Wolffs actual blood gushing down to his knees

Allegedly a trailer for the film was accidentally shown at a screening of Peter Rabbit (2018) in Australia. However, a very similar event supposedly happened in 2007, where a trailer for The Hills Have Eyes Part 2 was allegedly shown to a theatre full of small children ( source: moviefone.com/2007/04/06/theater-accidentally-shows-hills-have-eyes-2-to-little-kids/amp/ ) Similar stories have been reported several times since then, even reported by reputable news sources, with a graphic horror film allegedly being shown to a group of small children, who were at the theater to see a kids' movie. In all alleged instances, the theatre is said to give free movie vouchers for all present. The similarities of these stories have made some speculate that it is nothing more than an urban legend.

Ari Aster was heavily influenced by the film The Cook, the Thief, His Wife, and Her Lover (1989).

In Peter's first scene at school, the words "Escaping Fate" is on the chalkboard with the teacher discussing it. This is a reference to Halloween (1978), where the main character discusses the same thing in class. Appropriately, this movie was released the same day as the trailer for Halloween (2018).

This film is director Ari Aster's feature debut.

The entire interior of the Graham house was built on a sound stage.

This was the fourth A24 movie to get a wide release after The Witch (2015), Free Fire (2016) and It Comes at Night (2017).

Director Cameo (Ari Aster): the voice on the phone calling Annie about her exhibit date at the Archer Gallery.

The film premiered on January 21, 2018 at the 2018 Sundance Film Festival in the Midnight section.

Toni Collete (Annie) is actually 22 years younger than her on screen husband, Gabriel Byrne.

Filmed in Utah Film Studios in Park City Utah

Gabriel Byrne and Alex Wolff previously starred together in the television show "In Treatment".

Gabriel Byrne worked with Alex Wolff in the HBO tv series "In treatment" (2008-2010) also like father and son.

The language spoken during the "invocation" that is given to Toni Collette is a combination of Hebrew and Enochian.

Early in the film, Charlie cuts off a pigeon's head outside her school. This foreshadows Charlie's accidental decapitation later in the film.

Charlie is eating a Dove candy bar when she cuts off the birds head.

Toni Collette's character Annie says in group therapy that her mother had DID. This is the same disorder that Collette's character had in the series "United States of Tara."

Toni Collete starred in a Showtime show by Diablo Cody called United States of Tara in which she played a character who suffered from DID (dissociative identity disorder). In the movie, Annie Graham (Toni Collette) says her mom had DID.