Benevolent and immortal Guardians like North (Santa Claus), the Tooth Fairy, the Easter Bunny, and the Sandman protect the children of the world by spreading wonder, hope, and dreams. Each guardian has a unique gift and responsibility, fostering joyful experiences and guarding the innocence of childhood. Their harmonious existence, however, is threatened by the return of Pitch Black, the boogeyman, who seeks to instill fear and darkness in the hearts of children, undermining their belief in the Guardians and stripping them of their powers.

In response to this growing threat, the enigmatic Man in the Moon appoints Jack Frost, a carefree spirit with the ability to manipulate ice and snow, as the newest Guardian. Jack, a loner who amuses himself by creating winter fun for kids but struggles with his identity and purpose, is reluctant to join this esteemed group. As Pitch's shadowy influence spreads and children's beliefs waver, the Guardians must convince Jack to embrace his new role and band together to stop Pitch from engulfing the world in despair, ensuring that the light of children's belief remains strong.