Although the film takes place in Chicago and (briefly) Tokyo, it was filmed in Bulgaria, for economic reasons. The location of filming caused issues with the predominantly English speaking cast and crew, who couldn't speak Bulgarian, resulting in the need for several translators on set.
Is the first film in either The Grudge or Ju-on franchises to take place in chronological order. A staple of the series was that each film would employ non-linear storytelling, until this film.
The only film in the series that does not feature Toshio's pet cat, as the budget would not allow a cat to be used for the production (his meow can still be heard from Toshio's mouth however).
The cast were not allowed to see Aiko Horiuchi in person or getting dressed in the costume and makeup, so that when they were to film scenes where she's attacking them the actors' reactions would be authentic. Marina Sirtis, Shawnee Smith, and Johanna Braddy in particular recount being genuinely terrified when first filming with Horiuchi as Kayako.
The first feature-length film in either the Ju-on or The Grudge series not to star Takako Fuji as Kayako. This is also the first American Grudge film not to feature Takashi Matsuyama as Takeo, who only appears via archive footage. His spirit is said to have possessed Max however.