Greg (Zachary Gordon) is an eleven year old who is not looking forward to attending middle school (sixth grade). After playing a clever prank on him, his older brother Rodrick (Devon Bostick) gives him some advice about surviving in this new environment: don't stand out from the crowd and don't make a fool out of yourself. His clueless dad (Steve Zahn) and his proper mom (Rachael Harris) have no advice to offer; ditto for his younger brother Manny who is still being toilet trained. On the first day of school, Greg carefully chooses a seat next to his best friend Rowley (Robert Capron). But at lunch, no one allows them to eat at their table, so they must sit together on the floor with Fregley (Grayson Russell), a nerdy loser.

Greg keeps a journal where he charts his experiences. His major goal in middle school is to earn a slot in the class "favorites" in the yearbook. Whereas his buddy Rowley is his jolly and carefree self all the time, Greg is obsessed with status and winning the attention and approval of others. Naturally, a strategy aimed at success usually winds up as failure. Among the arenas in which he tries to excel are wrestling, the Safety Patrol, becoming a cartoonist for the school paper, and acting and singing in the play The Wizard of Oz.

Greg and Rowley encounter some bullies on Halloween while they are out in the rich part of town trying to gather as much candy as they can. But their friendship is shattered when Greg throws a football at Rowley who falls and breaks his hand. Much to Greg's dismay, this draws the attention of a handful of girls at school who want to sign his hand cast. In addition, Rowley is chosen as the cartoonist for the newspaper.

Diary of a Wimpy Kid is a clever, snappy, and delightful comedy about the adventures of a preteen boy whose small stature disguises his bold expectations of achievement in the eyes of his peers. It is directed with élan by Thor Freudenthal (Hotel for Dogs). The winning screenplay is based on the bestselling fiction novels by Jeff Kinney. The drama, narrated by Zachary Gordon, has the freshness and wit of the long-running TV series The Wonder Years. It is fun to watch Greg respond to the antics of two girls who interact with him: one who sees him as an arch-enemy and the other who sees him as a rebel in the making. Equally clever are the complications that arise in conjunction with a piece of moldy cheese that lies on the school's outdoor basketball court. The message is a fine one for preteen boys and girls to ponder: be yourself, cherish your friends, and don't waste any of your energy trying to win the attention or approval of others.