The film opens with a montage of scenes reflecting life in the 1990s, with heavy traffic, rushing commuters, and homeless people on the street. Larry Dittmeyer (Michael McKean), an unscrupulous real estate developer, explains to his boss that almost all the families in his neighborhood have agreed to sell their property as part of a plan to turn the area into a shopping mall. The only exception is one family, which prompts his angry boss to ask, "What's their story?" which leads into the opening blue-box credits of The Brady Bunch.
The concept of the film is that although it is set in the 1990s, the Brady family are still portrayed as their 1970s television incarnations and are unaware of the disparity between their lives and their surroundings. The parents, Mike (Gary Cole) and Carol (Shelley Long), are having breakfast prepared by their housekeeper, Alice (Henriette Mantel), while the six children prepare for school. Jan (Jennifer Elise Cox) is jealous of her elder, popular sister Marcia (Christine Taylor); Cindy (Olivia Hack) is tattling about everything she's hearing; Greg (Christopher Daniel Barnes) is dreaming of becoming a singer; Peter (Paul Sutera) is nervous that his voice is breaking; Bobby (Jesse Lee) is excited about his new role as hall monitor at school.
Cindy gives Mike and Carol a tax delinquency notice (which was earlier mistakenly delivered to the Dittmeyers) stating that they face foreclosure on their house if they do not pay $20,000 in back taxes. The two initially ignore the crisis, but when Mike's architectural design is turned down by two potential clients, he tells Carol that they may have to sell the house. Cindy overhears this and tells her siblings and they look for work to raise money to save the house, but their earnings are nowhere near enough to reach the required sum. Mike manages to sell a Japanese company on one of his dated designs, thereby securing the money, only for Larry to sabotage it by claiming that Mike's last building collapsed.
On the night before the Bradys have to move out, Marcia suggests that they enter a "Search for the Stars" contest, the prize of which is exactly $20,000. Jan, having originally suggested this and been rejected, runs away from home. Cindy sees her leave and tattles, and the whole family goes on a search for her. They use their car's C.B. radio, and their transmission is heard by Schultzy (Ann B. Davis, who played Alice in the original series), a driver who picks up Jan and convinces her to return home.
The next day, the children join the "Search for the Stars" contest with a dated performance that receives poor audience response compared to the more modern performances of other bands. However, the judges — Davy Jones, Micky Dolenz, and Peter Tork, all of the 1960s band The Monkees — vote for them, and they win the contest as a result. The tax bill is paid and their neighbors withdraw their homes from the market, foiling Larry's plan and securing the neighborhood.
The film ends with the arrival of Carol's mother (Florence Henderson, who played Carol in the original series), who finally convinces Jan to stop being jealous of Marcia, only for Cindy to start feeling jealous of Jan.
In the end credits, the Bradys are in their traditional blue boxes, but are updated for the time and include various humorous outtakes, such as Marcia taking over Jan's box, Alice removing her uniform to reveal bondage gear underneath, Mrs. Dittmeyer aggressively seducing the married (and seemingly smitten) Mike, and grandma coming into Carol's box.
- Ash Ketchum, Pikachu, Misty, Brock, Littlefoot, Cera, Ducky, Petrie, Spike, The Dazzlings, Dr. Facilier, Megan and Team Rocket guest stars in this film.
- The Dazzlings, Dr. Facilier, Megan and Team Rocket will work with Larry Dittmeyer in this film.
- Due the real film has some strong language and bad scenes, it's gonna be censored and cuts in this film, be sure this is kids film.