- Duchess – Madame Adelaide’s cat and mother of three kittens
- Thomas O’Malley (full name: Abraham de Lacy Giuseppe Casey Thomas O’Malley) – A feral cat who befriends Duchess and her kittens, becoming a father figure to the kittens and falling in love with Duchess.
- Marie – middle kitten; often imperious or snobbish to her brothers, but her mother’s especial companion.
- Toulouse – the oldest kitten, who idolizes all alley-cats and especially Thomas. He is also a talented painter.
- Dean Clark as Berlioz – the youngest kitten. He is somewhat timid and shy. He is also a talented pianist.
- Edgar Balthazar – Madame Adelaide’s butler who tries to get rid of the cats in order to inherit her fortune.
- Madame Adelaide Bonfamille – a former opera singer and owner of Duchess and her kittens.
- Georges Hautecourt – Madame Bonfamille’s lawyer: an eccentric, lively old man
- Scat Cat – Thomas’s best friend and leader of a gang of jazz-playing alley cats. Scat Cat plays the trumpet.
- The gang of alley cats includes
- Shun Gon – a Chinese cat, plays the piano and drums made out of pots.
- Hit Cat – an English cat, plays acoustic guitar.
- Peppo – an Italian cat, plays the accordion.
- Billy Boss – a Russian cat, plays the double bass.
- The gang of alley cats includes
- Roquefort – A house mouse and also a friend of the cats, who assists in the expulsion of Edgar.
- Frou-Frou – Roquefort’s horse companion, who subdues Edgar.
- Napoleon – a Bloodhound who attacks Edgar when he intrudes in the farm where Napoleon lives.
- Lafayette – a Basset Hound and Napoleon’s companion. He sometimes proves smarter than Napoleon, but is also more timid.
- Abigail Gabble – a goose who befriends the cats.
- Amelia Gabble – Abigail’s twin sister.
- Uncle Waldo – the drunken gander uncle of Abigail and Amelia.