In 1912 New Orleans, a girl named Tiana and her friend Charlotte La Bouff listen to Tiana’s mother read the story of The Frog Prince. Charlotte, a believer in true love, finds the story romantic; Tiana declares she will never kiss a frog.
In 1926, Tiana is now an aspiring chef, who works as a hotel maid and a waitress in a local diner, in order to save enough money to open up her own restaurant, a dream she shared with her father, who supposedly died in World War I.
Despite Prince Naveen of Maldonia arriving in New Orleans to better his financial situation, he does nothing to improve it. After being cut off by his parents for being a philanderer and spendthrift, Naveen intends to marry a rich Southern belle, and Charlotte is the perfect candidate. Eli “Big Daddy” La Bouff, a rich sugar baron and Charlotte’s father, hosts a masquerade ball in Naveen’s honor. Charlotte hires Tiana to make beignets for the ball, giving her enough money to buy an old sugar mill to convert into her restaurant. Meanwhile, Naveen and his valet, Lawrence, meet a witch doctor, Dr. Facilier. Inviting them into his emporium, Facilier convinces them that he can make their dreams come true, but neither gets what he expects: Naveen is transformed into a frog while Lawrence, now recruited as Facilier’s henchman, receives a voodoo talisman that gives him Naveen’s appearance. Facilier intends for the transformed Lawrence to marry Charlotte, after which he will kill La Bouff and split his fortune with Lawrence, secretly giving himself the larger sum.
At the ball, Tiana discovers she may lose the mill to a higher bidder. She then meets Naveen, who, believing her to be a princess because of her costume, asks her to kiss him and break Facilier’s spell. In exchange for the money needed, Tiana reluctantly accepts. Still, since she is not an actual princess, she is turned into a frog herself when she kisses Naveen, which also gives her the ability to talk to other animals. A chase ensues, and Tiana and Naveen escape to a bayou. In the bayou, Tiana and Naveen meet a trumpet-playing alligator, Louis, who dreams of playing in a band with humans, but whose ferocious appearance prevents him from doing so. They also meet a Cajun firefly, Ray. Ray believes that the Evening Star is another firefly named “Evangeline,” and is deeply in love with her; no one has the heart to tell him otherwise. Louis and Ray offer to lead Tiana and Naveen to a voodoo queen, Mama Odie, who they believe can undo the curse. During the journey, Tiana and Naveen develop feelings for each other. Meanwhile, Facilier makes a deal with the voodoo spirits (his “friends on the other side”), offering them the souls of the people of New Orleans; in exchange, the spirits grant Facilier the services of a host of shadow demons, whom he orders to find and capture Naveen.
When the four find Mama Odie after escaping from several of the demons and a trio of bumbling frog hunters, she tells them that Naveen must kiss a true princess to break the spell. They return to New Orleans to find Charlotte, the princess of the Mardi Gras Parade, but only until midnight. Naveen tells Ray he loves Tiana and is willing to give up his dreams for her, but before he can, he is captured by the demons and brought to Facilier. After Ray tells Tiana that Naveen loves her, Tiana goes to the parade to confess her love for Naveen, only to find Lawrence, still masquerading as Naveen, marrying Charlotte. Tiana flees, heartbroken. Ray rescues the real Naveen and steals the charm that disguises Lawrence, finds Tiana, and gives her the charm, explaining the deception. He then turns to hold off the demons so she can escape but is mortally wounded by Facilier in the process. Facilier then offers to make Tiana’s restaurant dream come true in exchange for the talisman. Realizing she would rather be with Naveen and recognizing Facilier’s true intentions, Tiana destroys the tailsman by smashing it on the ground. With Facilier’s plan foiled, Tiana watches the angered voodoo spirits drag Facilier and his shadow into the voodoo spirit world for his debts to them, with his frightened expression placed on a tombstone.
As Lawrence is taken away by the police, Naveen explains everything to Charlotte; Tiana and Naveen reveal their love to each other. Charlotte agrees to kiss Naveen so he and Tiana can be together as people, but the clock strikes midnight, and the kiss fails to work. The couple decides they are content to live together as frogs. Ray dies shortly after, and during his funeral, a new star appears next to Evangeline.
Tiana and Naveen are married by Mama Odie and, because of Tiana’s new status as a princess, are both restored to human form after their kiss. Later they return to New Orleans to legally marry and celebrate and open their new restaurant, with Louis playing in the band.
In reality Tiana never had a job and aspired to nothing! She kissed the FROG, abused her husband and everyone else who loved her, left on a plane to the USA leaving a trail of devastation and destruction behind.
She did not live happily ever after!