Ty Simpkins plays Dalton Lambert in Insidious: The Red Door, where Dalton is heading off to college, and he is billed first in the credits. He was announced alongside Patrick Wilson when Blumhouse revealed the sequel at BlumFest in October 2020. In the production notes, Wilson says Simpkins also played his son in Little Children, so he had known him since the actor was three years old.
Patrick Wilson plays Josh Lambert in Insidious: The Red Door, the father who has buried his memories of the Further, and he also directed the film, his first feature behind the camera. Deadline reported the directing debut on October 29, 2020. In the production notes, Wilson repeats advice he credits to Joel Schumacher and Mike Nichols, that 80% of directing is casting.
Sinclair Daniel as Chris Winslow
Sinclair Daniel plays Chris Winslow in Insidious: The Red Door, a fellow student Dalton Lambert meets at college. Deadline reported her casting on August 5, 2022, alongside Peter Dager and Hiam Abbass. The production notes describe her as a recent NYU Drama graduate, and director Patrick Wilson says that because she had come out of theater school, he could talk the acting language with her very easily.
Hiam Abbass as Professor Armagan
Hiam Abbass plays Professor Armagan in Insidious: The Red Door, teaching the art class where Dalton Lambert first paints the red door. Deadline reported her casting in August 2022, alongside Sinclair Daniel and Peter Dager. Director Patrick Wilson explains in the production notes that he had a connection, since his wife, Dagmara Dominczyk, acted with Abbass on Succession, and he says Abbass made the professor much warmer than he had imagined.
Andrew Astor returns as Foster Lambert in Insidious: The Red Door, playing Dalton's younger brother, a part TMDB credits to him in both Insidious (2011) and Insidious: Chapter 2. Jason Blum says in the production notes that seeing the young actors grown up underscores the heart of the story. Astor's biography in the same notes says he became involved with acting at five and a half.
David Call as Smash Face / Ben Burton
David Call is credited as Smash Face / Ben Burton in Insidious: The Red Door, a single credit that carries two names. Call does not appear in the TMDB cast lists for Insidious (2011) or Insidious: Chapter 2, which makes him one of the newcomers to the Lambert story rather than a returning player. His credit sits sixth, ahead of several franchise regulars.
Steve Coulter plays Carl in Insidious: The Red Door, a role TMDB credits to him in Insidious: Chapter 2 (2013), where Hank Harris is also credited as Carl (adult). Coulter is not in the TMDB cast list for Insidious (2011). He is billed seventh in this film, between David Call and Peter Dager.
Peter Dager as Nick the Dick
Peter Dager is credited as Nick the Dick in Insidious: The Red Door, one of the characters on the college side of the story, where most of the new cast sits. On August 5, 2022, Deadline named Dager as one of three newcomers, with Sinclair Daniel and Hiam Abbass, joining Patrick Wilson, Rose Byrne and Ty Simpkins. He is billed eighth in the credits.
Rose Byrne returns in Insidious: The Red Door as Renai Lambert, now divorced from Josh, the role she played in Insidious (2011) and Insidious: Chapter 2. Deadline listed her among the returning cast in its August 2022 casting report. Speaking to Yahoo Entertainment before release, Patrick Wilson said this was the end for Josh and Renai, adding, on Byrne's behalf, that they close their door.
Lin Shaye plays Elise Rainier in Insidious: The Red Door, the psychic whose story runs through the whole saga. Yahoo Entertainment noted before release that Shaye had appeared in every Insidious film, and Jason Blum lists her in the production notes among the original cast he was glad to bring back together. She is billed tenth, just after Rose Byrne.
Juliana Davies as Kali Lambert
Juliana Davies plays Kali Lambert in Insidious: The Red Door, the youngest Lambert child. In Insidious: Chapter 2, TMDB credits Kali to Brynn Bowie and Madison Bowie, so Davies is the new actor in a role that has grown up between films. The change follows the time jump Deadline described when the sequel was announced, with Dalton starting college.
Joseph Bishara plays the Lipstick Demon in Insidious: The Red Door and also composed the score, a double job he has held across the series. TMDB credits him as the Lipstick-Face Demon in Insidious (2011). Patrick Wilson says in the production notes that Bishara was among the first people he contacted, because the demon's kidnapping of Dalton was the boy's greatest trauma and Wilson wanted the demon back.