The movie begins with Eudora reading the Frog Prince to young Charlotte and young Tiana. Immediately after the book is over young Charlotte cheers and falls over in her over-poofy dress. She tortures her poor cat by sticking it in a sock that looks like a frog and trying to get Tiana to kiss it. Charlotte's dad, Big Daddy, walks in, and Charlotte begs him for a new dress. Big Daddy agrees after Charlotte begins to pull on his mustache. He tells Charlotte she would get that dress and that was it, then proceeds to give her a puppy.
Years later, Charlotte runs to Tiana while Tiana is working, and tells her that Prince Naveen is coming and she wants to impress him at the Mardi Gras ball, paying Tiana the rest of the money she needed for Tiana's palace for food for the ball. Charlotte overdecorates herself but is
still Tiana's best friend, telling her she looked absolutely beautiful in her Princess dress. When Naveen "arrives," Charlotte runs down to dance with him. At the gazebo, Lawrence, disguised as Naveen, proposes to Charlotte, and Charlotte immediately makes arrangements for their marriage on her parade float in the parade. (Her father is King of the Mardi Gras and can afford this.)
While Frog Tiana and Frog Naveen are trying to become human, Mama Odie tells them to become human they must kiss a Princess Mama Odie makes Charlotte the Princess, because her father was King of the Mardi Gras and she was a Princess until Mardi Gras ended at exactly midnight.
Charlotte is about to get married to Lawrence/Naveen when the frogs stop then and Charlotte discovers Lawrence's true identity.
Naveen/frog finds Charlotte and tells her to kiss him, but to help Tiana get her resteraunt. Then Tiana stops him, telling she would rather have him than a restaurant. Charlotte cries with happiness and tells Naveen that she'd kiss him, no marriage required. Then the clock strikes midnight and Naveen and Tiana stay frogs until they turn into humans on their wedding day. Charlotte is seen at their human wedding, catching Tiana's bouquet and taking an interest in Naveen's brother, even though he was only six-and-a-half.