Greg Heffley is a middle school student, the narrator of the story, and the main protagonist. Greg is the middle child with two brothers, and he lives with both his parents. Greg is impulsive, manipulative, and he makes choices that always serve his own interests. Above all else, Greg yearns to be popular, and throughout the novel, he consistently tries to achieve a higher social standing at school.

Greg is an underachiever, and he claims that his older brother taught him to “set people’s expectations real low so [he] end[s] up surprising them by practically doing nothing at all” (15). Greg is unwilling to do much work, but he still wants to reap the benefits of success and the accolades that come with it. This leads him to twist the truth to make it look like he did more work than he actually did, such as when he tricks his father into thinking he played outside by “[running] through the neighbor’s sprinkler a couple times to make it look like [he] was all sweaty” (27).

Greg often refuses to take responsibility for his own behavior, and he blames other people for the consequences of his own actions. He fails to study for a quiz in Geography because he is confident he will be able to cheat by looking at the map on the wall, and when a student reminds the teacher to cover up the map, Greg claims that “thanks to Patty, [he] ended up flunking the quiz” (94).