During a benefit concert in Paris, France, David Seville is injured from a backstage accident. Having to recuperate there, Dave asks his aunt, Jackie, to look after the Chipmunks, Alvin, Simon, and Theodore. Arrangements are also made for them to go to school at West Eastman High School. After Jackie also has an accident, the Chipmunks are left in the care of Toby, Jackie’s grandson.
Meanwhile, Ian Hawke, who is broke and destitute, lives in the basement of JETT Records. Three singing female chipmunks, Brittany, Jeanette, and Eleanor, also known as The Chipettes, emerge from a FedEx packagee. Ian recruits and hires the Chipettes in an effort to resurrect his career.
While at school, the Chipmunks are ridiculed by jocks, who threaten to kill them for drawing their girls’ attention away from them. They chase the Chipmunks around the school and give Simon a swirlie in a toilet. They visit the principal’s office, only to discover that the principal, Dr. Rubin is a huge fan, and enlists their help to raise money for a music program by participating in a contest. Meanwhile, Ian is shocked to find the Chipmunks on the front page of his newspaper. After he reads a story about them, he quickly sends the Chipettes to school.