Derek Thompson (DWAYNE JOHNSON) was once a great, professional hockey player. But a shoulder injury sent him to the minor leagues where he lost his on the ice mojo. Now playing for the Lansing Ice Wolves, Derek hasn't taken a shot on goal in nine years and isn't pleased about falling into the shadow of young upstart Mick Donnelly (RYAN SHECKLER). But he has proudly racked up more penalty box time than any other player, mainly due to his teeth-popping body hits that have earned him the nickname "The Tooth Fairy."
While he enjoys the attention that brings, he knows full well the fleeting nature of fame. Accordingly, he often dashes the dreams and aspirations of young people with a bitter reality check. Despite that and his self-centered nature, he's managed to attract a pretty single mom, Carly Harris (ASHLEY JUDD), as his girlfriend, and gets along well with her 6-year-old daughter, Tess (DESTINY GRACE WHITLOCK). Things are more strained, however, with her older guitar-playing brother, Randy (CHASE ELLISON), who wants nothing to do with him.
Due to squashing kids' dreams and nearly informing Tess that the Tooth Fairy doesn't exist after she loses one of her teeth, Derek wakes up one morning sporting fairy wings, a woman's tutu, and a summons from the Department of Dissemination of Disbelief. He's then magically transported to fairy headquarters where he meets leader Lily (JULIE ANDREWS) who's assigned Tracy (STEPHEN MERCHANT) as Derek's non-flying caseworker/instructor. Meanwhile, fairy Jerry (BILLY CRYSTAL) supplies the disbelieving hockey player with the tools of the trade, such as memory erasing dust, invisibility potion, shrinking paste, and items to deal with cats and dogs while in a miniature state.
Derek then learns that he must serve two weeks as the Tooth Fairy, summoned at any moment to sneak into a child's bedroom and leave money under their pillows in exchange for their recently removed teeth. To make matters worse, Derek can't tell anyone of his new duty, a matter that complicates both his time on the ice and his relationship with Carly and her kids. From that point on, he begrudgingly does his thing, all while learning about himself and the rekindled notion of never giving up on one's dreams.