The Radcliffe family and their one hundred and one dalmatians are preparing to move to their "Dalmatian Plantation," a home in the countryside with plenty of room for all of them. However, one of the puppies, Patch, feels ignored and wishes to be unique like his television hero, the German shepherd Thunderbolt. While watching the Thunderbolt Adventure Hour, Patch hears about a chance to appear on the show. Patch is accidentally left behind when his family leaves for the plantation, so he decides to head for the audition to meet his hero and win a guest spot on the show. Patch fails to impress the producers, allowing a jealous Lil' Lightning to manipulate the producers into making himself the hero of his own show. Depressed, Patch leaves and runs into Thunderbolt.
Elsewhere in London, Cruella de Vil has returned, but she is under probation and a restraining order for her past behavior. No longer allowed to maintain her previous lifestyle, she attempts to soothe her fixation on spots with the help of a German artist named Lars. In order to inspire him, she restarts her hunt for the dalmatians, using a newspaper picture of Patch to find their new address.
Patch's family finally becomes aware that he is missing and go back to London to find him. Cruella bails her former henchmen, Horace and Jasper Badun, out of prison. She sends them in a stolen dog food truck to steal the remaining puppies. The Baduns succeed after dealing with Nanny, and they take the dogs to Lars. When Cruella requests she be made a masterpiece from the puppies' fur, Lars refuses, not wanting the pups to be harmed. Angered, Cruella has him bound and gagged and returns to her original plan of making a dalmatian fur coat.
The captured puppies use the Twilight Bark to send a distress signal, which is picked up by Patch and Thunderbolt, and the two set out to save Patch's family. On the way, they encounter Lil' Lightning, who follows them and convinces Thunderbolt not to use Patch's stealth plan but to openly attack. Thunderbolt frightens the Baduns, but Cruella knocks him unconscious and he and Patch are captured. Lil' Lightning, believing his own scheme fulfilled, sneaks into the building and reveals that Thunderbolt is a fraud, and tells him that what he said a while ago was a lie to get him out of the way and finally be out of his shadow, before fleeing. Crushed by this revelation, and Thunderbolt telling Patch that he's really an actor, Patch falls into despair, but his brothers and sisters restore his spirit by reminding him that Thunderbolt escaped a similar predicament in one of the TV episodes. Patch breaks out and releases his family, but Thunderbolt remains behind, ashamed of himself for disappointing Patch. The dalmatians escape through the building's roof to the Cruella's Panther De Ville, while having the villains stalled on where they are. Meanwhile, Thunderbolt escapes from his cage and frees Lars.
Cruella and the Baduns discover the escape, and a chase ensues through the streets of London, crashing through the filming of Lil' Lightning's new show in the process, and having Lil' Lightning on the driving window. Cruella and the Baduns finally corner the dogs in an alleyway. Patch tries to hold them off while the others escape, but they are undaunted. Luckily, Thunderbolt arrives, having being driven to the scene by Lars, and fakes a heart attack, briefly gaining Lil' Lightning's sympathy and causing Cruella, in her distraction, to knock out the Baduns and incapacitate herself while Patch retreats back to the Cruella's car. He puts the Cruella's car in reverse, sending Cruella, the Baduns, and Lil' Lightning scrambling into the River Thames, along with their stolen van. As he and Thunderbolt stand triumphantly, Patch finally brings out a bark similar to Thunderbolt's bark.
The police arrest Lil' Lightning and the Baduns, while Cruella, now driven completely insane, is sent to a mental institute. The Radcliffes and Nanny who been told by Jasper and Horace it was Cruella who made them do it arrive, along with Patch's parents Pongo and Perdita, whom he introduces to Thunderbolt. The elder dalmatians thank Thunderbolt, but he dismisses himself as simply an actor. Patch, on the other hand, is, in Thunderbolt's eyes, "a real, one of a kind wonder-dog". After a newspaper montage reveals the fates of the characters, a post-credits scene shows Thunderbolt in his TV show with Patch as his new sidekick and the other puppies as extras, chasing the villain away into the sunset.
- Bobby Lockwood as Patch
- Barry Bostwick as Thunderbolt
- Susanne Blakeslee as Cruella De Vil
- Jason Alexander as Lil' Lightning
- Martin Short as Lars
- Samuel West as Pongo
- Kath Soucie as Perdita
- Jeff Bennett as Jasper Badun
- Maurice LaMarche as Horace Badun
- Rob Paulsen as Danny
- Tim Bentinck as Roger Radcliffe
- Jodi Benson as Anita Radcliffe
- Mary MacLeod as Nanny
- Ben Tibberas as Lucky
- Kasha Kropinski as Penny
- Tara Strong as Two-Tone
- Michael Lerner as the Producer
- "Seeing Spots"
- "Dalmatian Plantation"
- "The Thunderbolt Adventure Hour"
- "Canine Crunchies"
- "Cruella DeVil"
- "Try Again" (performed by Will Young)
- "Spots to Patches and Back Again" (performed by the Ying Yang Twins)
- "Doggs Gettin Down on London" (performed by Snoop Dogg, featuring Big Ben)
The film received positive reviews from critics. Rotten Tomatoes rating for this film is currently 67% "fresh" based on 6 reviews and with a rating of 5, but without a consensus.