The film, shot in Romania, continues the series' evolution from the pure horror genre of the first movie to a hybrid horror-comedy. It was the last Child's Play film to be released in theaters, with all future installments to be released direct to DVD. The film was followed by another sequel, Curse of Chucky, released on home video and Netflix in 2013.
Six years after the previous film, Glen, the kind and benevolent son of Chucky and Tiffany, has a nightmare in which he murders a little girl's parents. In reality, he is living a life of embarrassment and abuse as a ventriloquist's dummy. After being forced to perform and locked inside a cage, Glen sees Chucky and Tiffany on television.
Desperate to know his parents, Glen tracks Chucky and Tiffany down to Hollywood, where they are first shown killing a man who is dressed as Santa Claus for a movie. Glen manages to escape his abusive owner, hitch a ride on a truck, and mail himself in a box to California. He wakes up in the prop room of Jennifer Tilly's horror film, which includes the Chucky and Tiffany dolls. Glen uses the same voodoo amulet seen in previous films to bring them back to life. When Chucky (voice of Brad Dourif) finds out that Glen is his child, he faints. However, Tiffany (voice of Jennifer Tilly) is delighted and hugs her child. Chucky and Tiffany argue over whether Glen is a boy or a girl, due to his lack of genitals (though he is evidently a male). Chucky decides to continue labeling him as a boy, while Tiffany labels him as a girl, calling him "Glenda."
When a puppeteer Tony Gardner begins taking Tiffany apart, she and Chucky decapitate him with a piano wire, leaving Glen shocked and horrified. Jennifer Tilly sees the beheaded body and calls the police. Chucky, Tiffany and Glen ride home with her in a limousine. Glen, having witnessed his mom and dad kill the puppeteer, asks them why they murder others, as he feels that violence is bad. Chucky replies that it helps them to relax, but Tiffany, feeling parental responsibility, agrees with Glen and forces Chucky to join her in an attempt to stop killing people for the sake of their son. Chucky only pretends to agree, crossing his fingers behind his back, hoping to get Tiffany to shut up.
Jennifer tries to get a role as the Virgin Mary in Redman's directorial debut, but after he tells her that she isn't right for the part, she invites him over to her house. Chucky and Tiffany make plans to transfer their souls into Redman and Jennifer. Jennifer and Redman start to make love, only for Tiffany to knock them out. While they are unconscious, Tiffany uses a turkey baster to inseminate Jennifer with Chucky's semen.
Chucky leaves and takes Glen with him. After driving Britney Spears' car off the road, killing her, they proceed to go to a photographer's darkroom. The photographer, Pete Peters (John Waters), had taken pictures of Tilly kissing Redman and of Chucky masturbating. When Peters turns around, he notices Chucky is gone. Peters slowly walks around his lab looking for Chucky, who was hiding on a shelf. As Chucky is about to plan his attack, Glen tries to warn Peters that Chucky will kill him, only for Peters to bump into a shelf, causing a jar of sulphuric acid to fall into his head, accidentally killing him. Chucky, overjoyed with pride, believes Glen did this on purpose and takes a picture to celebrate, much to Glen's and Tiffany's dismay.
Jennifer awakens the next morning, realizes that she is pregnant and claims that Redman is responsible, though he denies this because, he said he had a vasectomy and refuses to have Tilly be in his next movie anymore because she's pregnant. Angered, Tiffany kills him. The next day, Jennifer is horrified to find herself with a fully pregnant belly. The voodoo magic that fuels the killer dolls has also accelerated the pregnancy. Jennifer is captured by Chucky. Her chauffeur, Stan, serving as Chucky's replacement body due to Redman's death, is also captured. Jennifer's assistant Joan (Hannah Spearritt) tries to help her, but she is brutally killed by Glen's murderous twin sister, Glenda, whose soul shares Glen's body. Tiffany discovers this and smacks Glenda to bring back Glen, who is horrified at what has happened.
Jennifer gives birth to twins, a boy and a girl, and it is then that Chucky has an epiphany. After years of being an infamous killer doll, Chucky finally accepts his circumstances. Disturbed, Tiffany rejects Chucky and resolves to take Glen with her. Chucky tries to throw a knife at Tiffany, but Stan jumps in front of it to save her, causing him to be stabbed in his chest, and he tells Jennifer that he loves her before he dies. The police arrive, forcing the dolls to flee. Jennifer is rushed to the hospital but claims she wants to see her babies. Tiffany drugs Jennifer and begins to possess her, but Chucky breaks in and kills Tiffany with an ax. Before Tiffany dies, she tells Glen to not make the same mistakes his mom and dad have made. Devastated by his mother's death, Glen finally snaps and challenges Chucky to a fight. Jennifer throws Chucky's axe to Glen, and Glen impales Chucky. Chucky assumes it's Glenda again, but Glen reveals that it's actually him, finally able to kill in revenge for his mother's death. As he says this, he brings the axe down, dismembering Chucky limb by limb, calling him "Daddy" and asking if he's finally proud of him. Chucky says that he is and he congratulates Glen right before the final, fatal blow. Realizing what he has done, Glen suffers an emotional breakdown and Jennifer comforts him.
Five years later, at Glen and Glenda's birthday party, a nanny quits her job because Jennifer's daughter Glenda scares her. Jennifer lets the nanny quit, only to kill her when she turns away. Jennifer's eyes glow green, revealing that Tiffany was successful in possessing Jennifer's body. Glen has one more birthday present to open, an anonymous gift. When he opens it, Chucky's severed arm springs up to grab Glen and Chucky's trademark laugh is heard as the screen goes black.
The movie was filmed almost entirely on the Castel soundstages in Romania. All of the animatronic and makeup effects were the handiwork of Effects Designer Tony Gardner (designer) and his company Alterian, Inc.
Seed of Chucky opened at #4 with $8,774,520 on November 12–14, 2004. When the film closed on December 23, 2004, the domestic gross was $17,083,732 and $24,829,644 worldwide.
In Australia, Seed of Chucky opened at #8 with $260,958 for the week of February 6–8, 2005 behind Million Dollar Baby (#2) and Sky Captain and the World of Tomorrow (#6). In Australia, Seed of Chucky was distributed by United International Pictures.
In France, Seed of Chucky opened at #11 with $694,948 for the week of March 2–8, 2005. It opened behind Le Couperet (#2) and the remake of Assault of Precinct 13 (#4). In France, Seed of Chucky was distributed by SND Distribution.
In the United Kingdom, Seed of Chucky opened at #10 with $202,022 for the week of May 13–15, 2005. It opened behind Monster-in-Law (#2), The Jacket (#8), and A Good Woman (#9). In the United Kingdom, Seed of Chucky was distributed by Momentum Pictures.
On Rotten Tomatoes, the film holds a Rotten 32% rating based on 75 reviews, with 23 fresh ratings. On Metacritic, it has an average score of 46, indicating mixed to average reviews.
Roger Ebert gave the film two stars out of four stating, "Seed of Chucky is actually two movies, one wretched, the other funny."
In June 2012, it was confirmed that a fifth sequel to Child's Play, Curse of Chucky, would be made and released direct-to-video, rather than theatrically. The new movie began production in early September of that year in Winnipeg, Canada and ended in mid-October. In November 2012, Don Mancini announced that filming for Curse of Chucky had been completed and the film was to be released by Halloween of 2013. Curse of Chucky went back to the Child's Play series' horror roots instead of being a dark comedy like the last two movies. Brad Dourif's daughter, Fiona Dourif, was featured in Curse of Chucky, and Brad Dourif reprised his voice role as Chucky. The film was released on home video and on Netflix.
A sixth sequel, Cult of Chucky, was planned to be released to home video and streaming services on October 20, 2017.