The movie was filmed at an actual abandoned church in France.
With the release of this film, director Michael Chaves has now directed most films within Conjuring - Die Heimsuchung (2013) Universe: Lloronas Fluch (2019), Conjuring 3 - Im Bann des Teufels (2021), and The Nun II.
(at around 37 mins) In the flashback where Sister Irene (Taissa Farmiga) says her goodbyes to Maurice (Jonas Bloquet), she gives him a bag of tomato seeds for his garden. This is because at the end of The Nun (2018), Maurice had said that he wanted to be a tomato farmer for a while, just like his father.
(at around 1h 9 mins) The painting of Valak is what Ed Warren was compelled to paint by a dream in Conjuring 2 (2016).
Joseph Bishara, who composed all past movies in the Conjuring Universe except for Annabelle 2 (2017) and The Nun (2018), was supposed to score the film but it was replaced by Marco Beltrami.