This film is the third installment of the Ju-on series. The film was preceded by two low budget films from 2000 known as (Ju-on: The Curse (2000) and Ju-on: The Curse 2 (2000)), whose storylines are continued in this sequel.

Toshio's spirit is often heard meowing throughout the film. Not only does this imply that his spirit merged with his deceased cat Mar, but it also relates to an old Japanese legend where the damned spirits of lost children become strays and as a result, produce a cat's meow.

It took 2 hours to apply the white makeup to Takako Fuji and Yuya Ozeki in order for them to play their ghostly incarnations of their characters.

Kayako and Toshio are based on the Japanese legend of the Onryo, a vengeful spirit that unlike western ghosts, can physically manifest to attack and kill victims whereas Western ghosts are just energy and can't physically appear. They manifest when they are killed in a state of deep rage as explained by the opening title card.

Yuya Ozeki is terrified of cats in real life, making filming any scenes with Toshio's pet cat Mar rather troublesome.

Sam Raimi helped Sony option the remake rights, as he was a big fan of this film, saying it terrified him.

The house used in the film was not a constructed set but a real location, which had to be rented for film production. It became a tourist attraction following the film franchise's popularity. The house was demolished in 2019.

In a form of irony, the reason the Saeki family have a black cat as a pet is because in Japanese folklore, it is said that owning a black cat will bring good luck and fortune, in stark contrast to their ultimate fates as vengeful ghosts.

Technically, this is the first film in the Ju-On series that received a theatrical release. The previous film, Ju-on: The Curse 2 (2000), had a very limited theatrical release before going straight to video.

The backstory that creates the curse in this series is strongly reminiscent of the myth of Oiwa, a traditional Japanese onryo (resentful ghost) legend. Oiwa was a housewife disfigured and brutally murdered by her unfaithful husband. She returns to haunt him and makes him murder his new lover. According to the legend, a curse accompanies her story, and that those who retell it will suffer injuries and even death. The disfigured aspect of the onryo is likely what inspired Sadako Yamamura's appearance in Ringu (1998).

Takako Fuji, Takashi Matsuyama and Yuya Ozeki would reprise their roles as the doomed Saeki family in the American remake The Grudge (2004). Ozeki had to be recast for The Grudge 2 (2006) as he had noticeably gotten older.

Included among the "1,001 Movies You Must See Before You Die" edited by Steven Schneider.

Author Kei Ohishi had written a novelization for the film to expand upon Kayako's backstory.

Ryota Koyama, who played Toshio in Ju-on (2000) and Ju-on: The Curse 2 (2000), had outgrown the role by the time production commenced and was recast with Yuya Ozeki.

Chikako Isomura's last film before her death of natural causes in 2006. Her likeness was used as a tribute to her in the film Ju-on: White Ghost (2009).

The only film in the Ju-on series that has Kayako wearing a different haircut compared to all the other films (including the American remakes). Although she is known for having long and straight jet-black hair, here she is wearing a short and wavy bob haircut at her shoulders with bangs.

Yôji Tanaka previously appeared in Ringu 0: Birthday (2000) featuring another iconic J-horror antagonist Sadako Yamamura. Both franchises would crossover in Sadako vs. Kayako (2016).

Shuri Matsuda would go on to appear in The Grudge 2 (2006), an American remake of the Japanese films.

Megumi Okina would collaborate with Masayuki Ochiai in the remake of Shutter (2008). He specifically cast her in the film as a fan of the Ju-on series. He would go on to direct the reboot of the Ju-On series, Ju-on: The Beginning of the End (2014).

Shuri Matsuda and Yukako Kukuri, who play Kazumi and Miyuki, are friends of Takashi Shimizu in real life, and cast them in the film as a result.

Kayako is not only based on the Japanese Onryo, she also has a spider motif to her ghostly appearance. She usually crawls out of the attic or small dark spaces, and spiders are known for hiding in dark and dusty corners of the house, she also sometimes crawls out of the trash bag Takeo stuffed her in, a reference to spiders bursting out of the cocoon of eggs. Kayako is basically impossible to avoid, as there's no way to rid yourself of the curse, a reference to the fact that it's nearly impossible for prey to escape a spider's web.

Being a ballet dancer and a trained contortionist, Takako Fuji performed all of the unnatural and seemingly impossible bends, snaps, and jerky movements that Kayako performs in the film, especially in the infamous staircase sequence. No special effects or CGI were used at any point.

The infamous scene where Kayako attacks a character from underneath the gap of her bedsheets was inspired by the old Japanese urban legend of The Girl in the Gaps, a ghost which is said to enter our world only through small gaps in the real world.

Final body count presented in film is 17, including the Saeki family and their cat.

Chronologically, Izumi's story and death takes place last. This is hinted at when Izumi's mother is seen watching a news report of Rika's death.

Saito, the sensitive old man Rika looks after is portrayed by Isao Yatsu, who reprises his role in The Grudge 2 (2006). He is credited only as the "Peek-a-boo Man". Yatsu is known for appearing in iconic Japanese horror films like Ringu 2 (1999) and Dark Water (2002).

Deleted scenes feature Takeo recreating his murder as a whole, taking Rika's corpse to the closet room (exactly like the curse led Katsuya to do, with the same shot), and stabs her, making her blood splatter on Kayako's photographs. Also, more shots of the empty town are seen. This scene was recreated in The Grudge 2 (2006) with Karen's sister Aubrey.

Though never explicitly stated or seen in the film, Yoko Toyama, Izumi's catatonic mother, is heavily implied to be deceased, likely claimed by the curse. This is hinted at when she's no longer around in her house once Izumi is being hunted down by Kayako and the ghosts of her dead friends.

In a deleted scene after Izumi has been dragged into the shrine by Kayako, Saori's, Chiaki's and Ayano's faces appear besides Toyama's and Izumi's faces. Shimizu explained he dropped the scene because he thought it would either be ridiculed or take the focus away from Izumi's death and place it on the entire group instead.

Izumi's deceased friends Saori, Ayano and Chiaki briefly appeared in voice cameos in the previous film Ju-on: The Curse 2 (2000) as a teaser for Izumi's subplot in this film.

Miyuki is the only other main character in the films that appears to survive by the end of the series (not including the reboots). Hiromi from the sequel is the second example. Although Chiharu does return for Ju-on: The Grudge 2 (2003), she eventually meets her demise in the film.