By the end of November 2018, ahead of the release of Spider-Man: Into the Spider-Verse (2018) the following month, Sony Pictures Animation had begun developing a sequel due to the "incredible buzz" surrounding the project. The sequel was to continue the story of Miles Morales / Spider-Man, working from "seeds [that were] planted" throughout the first film. Joaquim Dos Santos and David Callaham were set to direct and write, respectively, with Amy Pascal returning from the first film as producer.

The other producers of the first film—Phil Lord, Christopher Miller, Avi Arad, and Christina Steinberg—were all also expected to return in some capacities. The next month, Pascal revealed that the film would focus on Miles and Gwen Stacy / Spider-Woman, exploring a romance between the characters that was cut from the first film, and that the sequel would be a "launching pad" for a previously announced female-focused spin-off film featuring Gwen. Sony officially confirmed the sequel in November 2019, with Lord and Miller returning as producers and a release date of April 8, 2022, announced.

In December, Lord and Miller revealed that the film was being split into two parts: Spider-Man: Across the Spider-Verse (Part One) and (Part Two), because they had written the story they wanted to tell for the sequel and realized it was too much for one film. The sequels were renamed in April 2022, becoming Spider-Man: Across the Spider-Verse and Spider-Man: Beyond the Spider-Verse. Their release dates were shifted then, with Across the Spider-Verse pushed back to June 2, 2023. They added that the film had 240 characters and would take place across six universes.