The film is an adaptation of a 2010 graphic novel by writer Pierre-Oscar Lévy and artist Frederik Peeters called Sandcastle. When asked what inspired him to adapt the book to film, director M. Night Shyamalan explained: "The book gave me the opportunity to work through a lot of anxieties I had around death and aging, and things like my parents getting older."

The movie that Charles (Rufus Sewell) can not think of that stars both Marlon Brando and Jack Nicholson is The Missouri Breaks (1976). Its plot has no relation to this film.

Before production, M. Night Shyamalan screened two films for his cast and crew, which were said to be big influences on the style and tone that he wanted for Old. The first was Walkabout (1971) directed by Nicolas Roeg. The second was Picnic at Hanging Rock (1975) directed by Peter Weir. Shyamalan described them as "stories about human beings struggling against the overwhelming power of nature" - films where nature becomes something mysterious, overwhelming, almost supernatural.

Filmed in 2020, during the height of the global Coronavirus pandemic. Cast and crew had to be tested daily for potential infections. M. Night Shyamalan said of the production: "The main priority was to keep everyone safe and well. Despite all of us living and working together over a period of months, nobody became sick, which was fantastic."

M. Night Shyamalan was inspired by Australian New Wave films like Picnic at Hanging Rock (1975) for the freeze tag game that the kids play on the beach. The idea of kids freezing in time was meant to compare with the kids rapidly aging later in the movie.