Melissa Graps, the ghost girl, is played by a boy, billed as 'Valerio Valeri.'
Two weeks into filming, the producers ran out of money. Director Mario Bava and the cast agreed to finish the film without pay.
The original Italian main titles of the film list both Giovanna Galletti and Giana Vivaldi. "Giana Vivaldi" is, however, the pseudonym of Galletti herself.
According to a 1985 Bava retrospective written by Tim Lucas for Fangoria (issue #43), Kill, Baby...Kill! was conceived in part as a bet with American distributors that Bava could complete a film in 12 days. The 30-page script was then penned on the spot.
Portions of the music score for Kill Baby, Kill! were previously used in the earlier Mario Bava film, Blood and Black Lace (1964).