Morton Schmidt (Jonah Hill) and Greg Jenko (Channing Tatum) are classmates. Later, they met again in the police academy. They helped each other and finally graduated from the police academy and became good partners. Unfortunately, they could only be traffic police and catch gangsters. Later, they joined the police's undercover drug enforcement organization "21 Jump Street". Captain Dickon (Ice Cube) told them that their mission was to return to high school as undercover and find the person who provided drugs to students. At school, they learned that the students' drugs came from a man named Eric (Dave Franco), but the case was not that simple. At the same time, Schmidt also fell in love with Molly, a friend of Eric, and Jenko's chemistry teacher seemed to be quite interested in him. What will be the result of the two people's undercover investigation in school? This film is adapted from the TV series of the same name.