The wizard Vitruvius attempts to protect a superweapon called the "Kragle" from the evil Lord Business. He fails to do so, but prophesies that a person called "the Special" will find the Piece of Resistance capable of stopping the Kragle.
Eight and a half years later, an ordinary construction worker named Emmet Brickowski (whom are hanging out with) comes across a woman named Wyldstyle, who searches for something after hours at Emmet's construction site. When he investigates, Emmet falls into a hole and finds the Piece of Resistance. Compelled to touch it, Emmet experiences vivid visions and passes out. He awakens in the custody of Bad Cop, Business' lieutenant, with the Piece of Resistance attached to his back. There, Emmet learns of Business' plans to freeze the world with the Kragle, revealed to be a tube of Krazy Glue with the label partially rubbed out. Wyldstyle rescues Emmet and takes him to meet Vitruvius, explaining that she and the wizard are Master Builders capable of building anything they need without instruction manuals. She further explains Business' disapproval of such anarchic creativity, for which most of them are incarcerated. Though disappointed to find Emmet displays no creativity, Wyldstyle and Vitruvius are convinced of his potential when he recalls visions of a humanoid deity called "the Man Upstairs".
Bad Cop tracks down Emmet, Thomas, Twilight, the others, Wyldstyle, and Vitruvius. They are rescued by Wyldstyle's boyfriend Batman and taken to a council of the remaining Master Builders, who are unimpressed with Emmet and refuse to fight Business. Bad Cop and his forces attack and capture all the Master Builders except for Emmet and a few others. Emmet believes the Master Builders' weakness is that their individual creativity prevents them from working together. He devises a team plan to infiltrate Business' headquarters, but he and his allies are captured and imprisoned, while Vitruvius is decapitated by Lord Business. With his dying words, Vitruvius reveals he made up the prophecy. Business throws the Piece of Resistance off the edge of the universe, sets his headquarters to self-destruct, and leaves the Master Builders and Bad Cop to die. Vitruvius' ghost appears before Emmet and explains it was not the prophecy, but his self-belief that made him the Special. Tied to the self-destruct mechanism's battery, Emmet flings himself off the edge of the universe to save his friends, who escape further danger with the aid of Bad Cop. Inspired by Emmet's sacrifice, Wyldstyle rallies the Lego people across the universe to use whatever creativity they have to build machines and weapons to fight Business' forces, with the Master Builders leading the charge.
Emmet finds himself in the real world, where the events of the story are being played out within the imagination of a boy, Finn, on his father's Lego set in a basement. The father—revealed as "the Man Upstairs" and Finn's inspiration for Business—chastises his son for ruining the set by creating hodgepodges of different characters and playsets, and proceeds to permanently glue his perceived perfect creations together. Realizing the danger his friends are in, Emmet wills himself to move and gains Finn's attention. Finn returns Emmet and the Piece of Resistance and fights his way onto Lord Business' ship. In the real world, Finn's father looks at his son's creations again and is impressed. Realizing Finn based the villainous Lord Business on him, the father has a change of heart and allows his son to play with his Lego however he sees fit. In the Lego world, Emmet tells Business that he, too, is special, as is everyone. Moved by Emmet's speech, Business caps the Kragle with the Piece of Resistance and unglues his victims with mineral spirits. As Emmet celebrates with his friends, alien Duplo beings beam down and announce their invasion as a result of the father allowing Finn's younger sister to play with his Lego sets.
- Duke will guest star in this film.
- The storyline continues in Thomas and Twilight Sparkle's Adventures of The Lego Batman Movie.