Sharpay Evans (Ashley Tisdale) performs a dance number at the Lava Springs Country Club ("Gonna Shine"). There she meets a famous producer Jerry Taylor (Pat Mastroianni) who offers her dog Boi a chance to star in his newest show on Broadway. Sharpay later convinces her father to let her move to New York City on her own. He hesitantly accepts but he has a condition: if the plan backfires, Sharpay is forced to move back with her parents. While in New York, Sharpay is kicked out of her penthouse because they don't allow dogs.
While in desparity, she meets Peyton (Austin Butler) who offers her a studio appartment. Sharpay accepts but is disgusted to find out what it is. Sharpay, Peyton, and Boi go shopping to give her studio a little makeover. While Peyton sees Sharpay in distress, he brings her to the stage of the Radio City Music Hall which makes her feel much better. There she meets Neal Roberts and Gill Samms, producers of Jerry's show. When she finds out they only want Boi. She auditions him but only to be caught in a tie with very competitive Roger Elliston (Bradley Steven Perry) ("My Boi and Me"). Minutes later, Sharpay meets Amber Lee Adams, the star of the show.
Leaving the theater, Sharpay is threatened by Roger that if she doesnt drop out, there will be serious consequences. Later in the film, Boi and Countess (Roger's female pup) run away together. Sharpay and Roger team up to find them. Fortunately, Peyton finds them digging through a trash can.
Meanwhile, Amber Lee fires her assistant and dimwittingly hires Sharpay just to boss her around. Unknowingly, Sharpay is a maid to her and answers to her every need. Sharpay later finds out that Amber Lee isn't all who she cracks up to be. So she and Roger concoct a plan to get her fired from the show. Her plan works, only to get both Sharpay and Amber Lee banned from the theater. Peyton shows footage to the producers that she can be the girl to star in the show ("New York's Best Kept Secret"). They take his word and hire Sharpay as the lead role in "A Girl's Best Friend". Sharpay accepts the offer only if Boi and Countess split the role of Shelby.
Sharpay and Peyton share a kiss and she finally gets her dream of performing on Broadway ("The Rest Of My Life")..