In a city resembling New York, a dog named Chuffie is abandoned on a bridge by his owner and saved from the traffic by a street dog named JD. A motorcycle gang passes over them and a parrot named Emmo is blown off one of the bikes and lands in JD and Chuffie's camp under the bridge. In order to dissuade the dogs from eating him, Emmo leads them to the mansion of owner Miss Lilly, a rich elderly animal lover. Miss Lilly is overjoyed by Emmo's return and lets JD and Chuffie stay with them and her three other dogs, Sherman, Velvet and Bella.
JD and Chuffie quickly acclimate to their new home (with JD falling in love with Bella), the only dark spot being Miss Lilly's greedy niece and nephew, Hannie and Ronnie. The twins are constantly trying to get their aunt to move to a rest home so that they can acquire her mansion and use it to throw parties where they can rub elbows with the rich and elite, but are rebuked every time.
One night, Miss Lilly suddenly dies and in the reading of her will, her attorney announces that her fortune and mansion all go to her pets. Enraged, Ronnie and Hannie drive to the library and spend the whole night going through lawbooks until they find a loophole: if the pets leave the property for 48 hours, they'll lose the inheritance and it will go to the twins. Upon this discovery, the two recruit a veterinarian goose named Dr. Quack to help them in getting rid of the pets.
Back at the mansion, the pets have let their newfound wealth go to their heads and spend it all on themselves. Disheartened by this, JD leaves on Miss Lilly's motorcycle. After his departure, Dr. Quack arrives with a fleet of limos to take the pets to their dream careers but it's all a trick: Bella is locked up in a ship where she's to be shaven for coats, Velvet is abandoned in a dark alley, Sherman is taken to a dogfighting ring where the losers are turned into meat, Chuffie is taken to a lab to be a test animal and Emmo is thrown out of a helicopter where he ends up clinging to a skyscraper's lightning rod for dear life. The twins barricade themselves in the mansion to wait out the deadline.
Eventually, Emmo is blown off the skyscraper and lands under the bridge, where JD is. Emmo tells JD everything and they capture Dr. Quack and force him to lead them to where the others are. They rescue Velvet, Chuffie and Bella while Sherman is rescued by Miss Lilly's old bike gang and is reunited with them later. Having learned what Ronnie and Hannie are up to, the pets head off to get their house back.
The group is able to sneak in through the attic and attempt to drive the twins out, first by Emmo pretending to be Miss Lilly's ghost then Sherman pretending to be rabid. Unfortunately, Ronnie and Hannie see through both ruses and are able to get the pets out the mansion's gate. They lament their fate until JD notices that Chuffie isn't with them.
In his room, Chuffie finishes his life-size space capsule model and rolls it down the stairs where Ronnie and Hannie run inside it. Chuffie then launches the capsule out of the house where it crashes on the street. At the moment, the deadline ends and JD says they've won, as Chuffie and Emmo are both inside the house. Miss Lilly's attorney arrives with the police and has the twins arrested for trespassing.
The pets reenter the mansion where Miss Lilly's spirit speaks to them, saying she now inhabits the house and asks that they make it into an animal sanctuary. They repair the mansion and make it into a sanctuary. Once they finish, animals of all kind come to stay. JD comments that they'll have a full house tonight but Bella tells him it won't be just tonight.
