The film marked the film debut of Josh Hartnett, who played Laurie Strode's son John.

Before H20's story was settled, an earlier treatment by Daniel Farrands called 'Michael Myers: Lord of the Dead' would have had Tommy Doyle uncover a town-wide conspiracy in Haddonfield to control Michael Myers, drawing comparisons to The Wicker Man and Rosemary's Baby.

Another discarded pitch, Robert Zappia's 'Halloween 7: Two Faces of Evil' (later 'Halloween: Blood Ties'), was originally meant as a direct-to-video film about Michael stalking an all-women's boarding school with a copycat killer twist compared to The Silence of the Lambs.

The film's story was developed by Scream writer Kevin Williamson under the working title 'Halloween 7: The Revenge of Laurie Strode,' and his original treatment included a scene where a student's class report on Michael Myers reveals the death of Laurie's daughter Jamie, prompting Laurie to vomit in a restroom.

John Carpenter was originally considered to direct at Jamie Lee Curtis's request to reunite the original team, but he demanded a $10 million fee plus a three-picture deal with Dimension Films, which the Weinsteins refused, leading Steve Miner to take over as director.

Jamie Lee Curtis later said she regretted doing the film, stating in a 2018 interview that she wished she had insisted Debra Hill produce it or she wouldn't have signed on.

Because producer Moustapha Akkad had a contractual clause preventing the writers from killing off Michael Myers permanently, Curtis nearly left the project weeks before filming until Kevin Williamson devised the paramedic storyline explaining Michael's survival, which convinced her to stay.

The first shot of Michael Myers in a paramedic uniform, later used in Halloween: Resurrection, was actually filmed the day after H20's principal photography wrapped.

Dr. Loomis's voice-over monologue reused from the original 1978 film could not be isolated from its old soundtrack, so sound-alike voice actor Tom Kane re-recorded it instead of using Donald Pleasence's original recording.

The closing credits' in memoriam tribute to Donald Pleasence misspells his surname as 'Pleasance.'

Dimension Films chief Bob Weinstein was dissatisfied with John Ottman's original score and had it supplemented during post-production with music from Marco Beltrami's scores for Scream, Scream 2, and Mimic, plus new Beltrami cues written during final sound mixing, much to Ottman's displeasure.

The song 'What's This Life For' by Creed was added at Bob Weinstein's insistence and appears both during a party scene and over the end credits.

A subtle tribute to Bernard Herrmann's Psycho score plays as Janet Leigh's character Norma Watson walks to her car, which is the same model car Leigh's character drove in Psycho.

Filming took place from February 18 to April 20, 1998, with Hillcrest Academy shot at the Canfield-Moreno Estate in Silver Lake, Los Angeles, and other scenes filmed in Melrose Hill, La Puente, Chatsworth, and Canoga Park, California.

Until the 2018 Halloween film's release, H20 was the highest-grossing film in the franchise, selling over 11.7 million tickets and outselling the previous three sequels combined.