On 13 December 2024 Jennifer Love Hewitt officially announced she would be returning as Julie James in the new sequel.
On 23 September 2024, Freddie Prinze Jr. announced he signed on to reprise his role as Ray Bronson in the new sequel.
Jennifer Kaytin Robinson confirmed the movie would not ignore the events of I Still Know What You Did Last Summer (1998).
Brandy Norwood, who played Karla in I Still Know What You Did Last Summer (1998), wanted to reprise her role in the sequel.
In 2014, director Mike Flanagan and writer Jeff Howard revealed plans for a reboot of I Know What You Did Last Summer (1997). In a 2016 episode of the "Shockwaves" podcast, Flanagan said the film would not having any connections to the 1973 novel nor the 1997 film, and the scope of the film necessitated an estimated budget of $15-20 million. This planned film eventually fell through, and instead a TV series reboot was released, I Know What You Did Last Summer (2021).