In 1912 New Orleans, a woman is reading a story to her daughter, Tiana, and her daughter's friend, Charlotte La Bouff, about the Frog Prince. Charlotte finds the story romantic, while Tiana proclaims she would never kiss a frog. Years pass by, and Tiana becomes a beautiful young woman who works two jobs so she can save money to start her own restaurant, fulfilling her late father's dream.
Elsewhere, Prince Naveen of Maldonia arrives in New Orleans determined to better his financial situation. Meanwhile, elsewhere in the city, The TARDIS Team having just arrived in New Orleans go to Duke's Cafe to eat breakfast and there they meet Tiana and After being cut off by his parents, Naveen is forced to marry a rich southern belle. It soon becomes obvious that Tiana's best friend and the rich sugar baron's daughter, Charlotte LaBouff, is the perfect candidate. Meanwhile, Naveen and his valet Lawrence run into the shady Dr. Facilier, a voodoo doctor and one of Malefor's new personal bounty hunters. Inviting them into his emporium, Facilier convinces the pair he can make their dreams come true. However, neither man gets what he's expecting; Naveen becomes a frog, while Lawrence is given a voodoo charm that makes him look like Naveen. Facilier intends for Lawrence to marry Charlotte, after which he will kill Big Daddy La Bouff and claim his fortune.
At the ball, Charlotte flirts with "Naveen" as Tiana learns she may lose the mill to a higher bidder. Adding insult to injury, her costume is accidentally ruined. Charlotte gives Tiana a princess costume and a tiara so she can rejoin the ball. After Charlotte returns to the party, Tiana makes a wish on the Evening Star, only to find a frog sitting next to her. The frog is Naveen, who asks Tiana (believing that she is a real princess) to kiss him and break Facilier's curse. Tiana agrees, in exchange for the money needed to outbid the other buyer. However, instead of Naveen turning into a human, Tiana is turned into a frog herself. As they escape Doctor Aaron and his crew see her being chased and help her escape. The TARDIS Team and The pair narrowly escape to a bayou, where they encounter Louis, a trumpet-playing alligator who longs to be human, and Ray, a Cajun firefly who longs for a sparkling light he calls Evangeline. They offer to lead them to the good voodoo priestess Mama Odie, who can undo the curse. Along the way, Tiana and Naveen begin to develop feelings for each other. Meanwhile, Facilier makes a deal with the voodoo spirits, offering them the souls of the people of New Orleans in exchange for finding Naveen for his plan and getting the Time Lord for Malefor.
Mama Odie tells Doctor Aaron, Cynder, Batty Koda, Louis, Ray, and the frogs that Naveen must kiss a princess in order for them to become human. Tiana and her friends return to New Orleans to find Charlotte, the princess of the Mardi Gras Parade. Naveen tells Ray he loves Tiana and is willing to give up his dreams for her, but before he can tell her directly, he and the Zeroth Doctor are taken by the demons and brought back to Facilier.
After Ray and the others tells Tiana that Naveen truly loves her, Tiana goes to the Mardi Gras parade only to find "Naveen" marrying Charlotte. Tiana escapes to a graveyard to be alone, while Ray, Louis and the others are able to rescue the real Naveen and Doctor Aaron and steal the charm. Ray finds Tiana and the others and gives her the charm and attempts to hold off the demons so she can escape, but Dr. Facilier mortally wounds him. Facilier confronts Tiana and offers to make her restaurant dream come true in exchange for the charm. Realizing she would rather be with Naveen, Tiana refuses and snatches the charm from Facilier and destroys it. The angered spirits claim Facilier himself as payment for his debts and his plan to get the Zeroth Doctor and his crew for Malefor and drag him into Malefor's world of shadows forever.
Naveen and Doctor Aaron are explaining the situation to a bewildered Charlotte when Tiana finds them both. Tiana reveals that she loves Naveen and would spend the rest of her days as a frog to be with him. Moved by this, Charlotte says she will kiss Naveen anyway so he and Tiana can be together. But the clock strikes midnight before she can kiss him. Louis then meets up with the frogs and the others, holding a dying Ray in his hands. Despite what happened, Ray shows happiness for the two before he dies. A funeral is held for Ray, after which another star shines brightly next to "Evangeline."
Contented to live together as frogs, Tiana and Naveen are wed by Mama Odie. As they kiss, they are turned into humans, because through their marriage, Tiana is now a princess. The two and the others return to New Orleans where everyone celebrates the wedding and Tiana and Naveen finally buy the restaurant. “Tiana's Palace” holds a gala opening, underneath the two shining Evening Stars. Doctor Aaron and his crew bid their new friends farewell as they depart on a another adventure.