Set in Paris, France in the year 1910, this is the story about a cat named Duchess and her three kittens: her daughter Marie, and her two sons Berlioz and Toulouse. They live in the Mansion of retired opera singer Adelaide Bonfamille, along with Edgar Balthazar (her butler), Frou Frou the horse, and Roquefort the mouse, who is a good friend of the cats.
Adelaide, who will be passing away soon, wants to settle her will with her lawyer Georges Hautecourt. Adelaide tells Georges that she wishes to leave her entire fortune to her butler, but only after her cats reach "the end of their natural lifespans." Edgar overhears this plan and is dismayed as he worries that he will die before he is able to collect the inheritance.
That evening, Edgar drops some sleeping pills in the cats' milk, putting them to sleep. Then, after night falls, Edgar takes the sleeping cats in their basket far away from home, hoping to drop them on the banks of a river near a farm.
The Aristocats and a host of other animals embark on an adventure that will lead them back home.