Rahul Kohli and Mike Flanagan's love of "Joel Miller" from The Last of Us (2013) inspired "Sheriff Hassan's" dress sense.
In Mike Flanagan's previous work Das Spiel (2017), "Jessie" portrayed by Carla Gugino throws the book with the title "Midnight Mass" at the dog, which is also the name of the book "Maddie" Kate Siegel was writing in Still (2016).
"Crockett Island" is modeled on remote Tangier Island in Chesapeake Bay, which also has an abandoned neighbor called the Uppands (here called the "Uppards".) Crockett is one of the most prominent family names on Tangier.
Some Christopher Pike books are seen on a shelf in "Riley" Zach Gilford's room. Mike Flanagan's next project is based on a Christopher Pike novel titled "The Midnight Club".
Mike Flanagan stated in several interviews and posted on Twitter that "Midnight Mass" was something he had always wanted to make. He also stated that the entire series was filmed with everyone having to follow quarantine procedures because of COVID-19. He personally thanked everyone involved in the project.