As the Smurfs get ready for the Blue Moon Festival, Papa Smurf sees in his cauldron a vision of Clumsy Smurf reaching for a dragon wand and the Smurfs in cages while Gargamel laughs. Not wanting this vision to come true, Papa Smurf disallows Clumsy to pick Smurf Roots. Clumsy disobeys Papa and ends up unintentionally leading Gargamel and Azrael to the village. The Smurfs all flee for their lives while Clumsy unknowingly runs towards the Forbidden Falls, with Papa Smurf, Smurfette, Grouchy, Brainy Smurf and Gutsy running after him. They find him at the edge of a cliff, and while trying to help him up, they are sucked into a gigantic vortex that spirits them to present day New York City. To make matters worse, Gargamel and Azrael follow them through the vortex. The Smurfs end up in the apartment of Patrick and Grace Winslow, a married and expectant couple, and their Basset Hound Elway. After introducing themselves and explaining their situation, the Winslows befriend them and allow them to stay in their apartment. The next day, needing to find a "star gazer" (a telescope), the Smurfs follow Patrick to his workplace at Anjelou Cosmetics, misunderstanding the previous explanation of his job as fortune-telling. He calls Grace to pick them up.
In preparation for her birthday celebration, the Smurfs read the story of Smurfette, how she was created by Gargamel to destroy them, only for Papa Smurf to rescue her and turn her fully into a Smurf. Meanwhile, she is having nightmares about reverting to her original form and betraying her fellow Smurfs by turning them over to Gargamel. The Smurfs are preparing a surprise party, but as Smurfette tries to find out what her fellow Smurfs are planning, none of them are saying a word. She takes this to mean that everyone has forgotten her birthday.
In Smurf Village, the Smurfs live peacefully among themselves and their leader is Papa Smurf. Some of the Smurfs include Clumsy Smurf, Brainy Smurf, Hefty Smurf and Smurfette, who was created by Gargamel from a lump of clay, but redeemed by Papa Smurf and became part of the village. Gargamel makes it his mission to capture the Smurfs, steal all of their essence, and become the most powerful wizard in the world.