This film is based on the best-selling children's book series of the same name by American writer Jeff Kinney. Gray Hofley (Zachary Gordon), who enters junior high school on his first day, is uneasy and desperately wants to stand out and become a star in the class yearbook. Gray's brother Roderick (Devon Bostick) gave him a lot of advice that he couldn't do this or that, but his good friend Raleigh Jefferson (Robert Capron) disagreed and continued to use the same clothes, language, and attitude he had in elementary school, which gave Gray a headache. Gray refused the invitation of girl Angel (Chloe Moretz) to join the school newspaper and took Raleigh to join the school security patrol. Gray made a mistake while avoiding the three thugs he had offended on Halloween, but lacked the courage to admit that he had taken the fall for him. Subsequent events worsened, Gray's popularity at school plummeted, and even his friendship with Raleigh was in jeopardy...