In the film, Dinah is Alice's cat. She is first seen sitting with Alice in a tree and listening to Alice's sister read from a history book. Alice then makes a crown out of flowers and puts them on Dinah's head, crowning her the flower girl cat. Then Alice's sister tells Alice to pay attention to her history lesson. Alice refuses to because the book has no pictures in it and tells her sister that in her world there would be books with nothing but pictures in it. Her sister believes this is nonsense. When Alice hears this, she picks up Dinah and tells her that in her world everything would be nonsense, because everything would be what it isn't. For example, animals would talk and live in houses because Alice's World would be a Wonderland. Then Dinah and Alice spot a White Rabbit with a coat on and a pocket watch and they chase after him to the Rabbit Hole. Alice falls down and waves goodbye to Dinah as she falls. Dinah is later mentioned by Alice at the Tea Party with The Mad Hatter, The March Hare, and The Dormouse which frightens him when he hears that Dinah is a cat. Dinah is finally seen at the end when Alice awakens from her dream. Alice picks her up and takes her home for tea along with Alice's sister.
A test cel setup of Alice, Dinah, and the Sister from the final scene of the film shows that Dinah was a black cat, not orange. Also, in a Big Golden Book by Al Dempster, the colored image of Dinah shows her as a black cat. Early designs for Dinah were lifted directly from a Figaro model sheet.