- It is a direct sequel to Insidious (2010) and Insidious: Chapter 2 (2013), and serves as both the fifth installment in the Insidious franchise.
- In February 2022, Wilson confirmed that location scouting had begun with filming set to begin in the Spring of that year. Principal photography for the film began in August 2022.
- Filming took place in Morris County, New Jersey, including in Morristown, Chatham, Florham Park, and at Drew University and other locations in Madison.
- Rose Byrne, Patrick Wilson, Andrew Astor, and Ty Simpkins reprise their roles from the films. Hiam Abbass and Sinclair Daniel also join the cast.
- Patrick Wilson’s directorial debut.
- The film was initially set to be released under the title Insidious: Fear the Dark, before it was announced in March 2023 that it was changed to Insidious: The Red Door.
- After the release of Insidious: The Last Key in 2018, Blumhouse Productions opted for possibilities to produce future films in the franchise, including a crossover with the Sinister series.
- The movie marks the return of Lambert family since Insidious: Chapter 2 (2013), and after that Insidious: Chapter 3 (2015) and Insidious: The Last Key (2018) are prequels set before Insidious (2010).
- Set 10 years later after the events of Insidious: Chapter 2 (2013), premiered exactly 10 years prior this movie.
- Insidious: The Red Door was theatrically released in the United States by Sony Pictures Releasing on July 7, 2023. The film has received mixed reviews from critics and was a commercial success, having grossed $188 million worldwide, becoming the highest-grossing film of the series.