Larry Daley, a down-on-his-luck divorced father struggling to make ends meet and stay connected to his young son, takes a job as a night security guard at the Museum of Natural History in New York City. On his first night, Larry is shocked to discover that an ancient Egyptian curse brings the museum to life after sunset. The exhibits, including a playful Tyrannosaurus Rex skeleton, a mischievous capuchin monkey, and a wax figure of Teddy Roosevelt who becomes his guide, turn his job into a wild adventure. As he navigates the chaos, Larry realizes he must take control of the situation to protect these historical figures and secure his job.

Facing the challenge head-on, Larry embarks on a quest to understand the curse and how to manage the nightly havoc in the museum. Alongside historical figures like Jedediah and Octavius, miniature leaders from the Wild West and Roman Empire respectively, Attila the Hun, and Sacagawea, Larry learns the importance of courage, responsibility, and friendship. His endeavors not only aim to preserve the safety and order of the museum but also to regain the respect and affection of his son, proving himself to be a hero in his eyes. These experiences at the museum teach Larry valuable life lessons, transforming him in ways he never expected.