Land of the Lost science fiction action story about a conceited, but down on his luck paleontologist, Dr. Rick Marshall(Will Ferrell) and his quest to prove time warps. He is disgraced after his awful interview with Matt Lauer. The only job he can find is working at the La Brea Tar Pits. Beautiful Holly Cantrell(Anna Friel) comes into Dr. Marshall's life and convinces him to proceed with his theory of time warps. She is the only one that believes in him. She encourages him to build the tachyon amplifier. After a night of binge eating, he finishes it. They head over to a sideshow attraction cave and gift shop. The owner Will Stanton(Danny McBride)unknowingly takes them into the cave where one of the time warps is about to happen. During the time warp, the tachyon amplifier is lost. The three find themselves in a desert of lost items from different time periods proving that time warps do exist.
They come across dinosaurs, giant bugs, and befriend a creature named Cha-Ka. He becomes their guide in the mythical land. Grumpy, the T-rex becomes a thorn in Dr. Marshall's side when he hears him say that he has the brain the size of a walnut. While in this land, Dr. Marshall receives a telepathic message from Enik claiming he is in trouble. The Sleestaks captured him and are planning to take over the world, but if Dr. Marshall brings the tachyon amplifier, the world can be saved.
The group witness the tachyon amplifier takes off with a Pteranodon and land in the middle of a nest. Only through impressive singing, does Dr. Marshall retrieve the tachyon amplifier. Holley discovers that Enik is not who he says he is, he was exiled because he was trying to take over the world. Before she can tell Dr. Marshall, she is taken by the Sleestaks. Seeing that world is about to end and the Sleestaks are against them, Dr. Marshall makes amends with Grumpy and save the world.
Will decides to stay with Cha-Ka in the other realm and Dr. Marshall has another interview with Matt Lauer that is a smashing success.