The film was shot in just three weeks.
The film was originally going to be named "The Further."
Thirty-three violins were used for the theme music.
In 2015, there was an Insidious-themed maze at Universal Studios, Orlando for the annual event of Halloween Horror Nights. The maze was based on the three "Insidious" films released at the time.
James Wan, who directed both this film and Insidious: Chapter 2 (2013), and The Conjuring (2013) and The Conjuring 2 (2016), had The Conjuring in mind, while directing the first Insidious movie. A number of coherent points can be spotted in both the first and the second Insidious movies.
James Wan: [puppet] (at around 30 minutes) When Josh is in the classroom, on the chalkboard behind him, the name "James Wan" can be clearly seen, as well as a drawing of Billy, the puppet from James Wan's Saw (2004), with the number "8" written under it. The rest of the names are the actual names of people that worked on the film.