Background: Relatively little is known about how perceived weight controllability influences important psychological health factors among adolescents. Thus, the purpose of this study is to explore adolescents' weight controllability beliefs and how those beliefs influence weight-related attitudes and behaviors. Methods: Adolescents (N = 369, mean age = 13.14, SD = 0.95) enrolled in physical education completed a survey packet, which included demographic questions and items targeting obesity, body shape, and weight controllability beliefs. Results: Participants believed that fat children have weight problems because they consume too many calories, are lazy, have access to junk food, and lack self-control. Those who endorsed high weight controllability beliefs were more likely to indicate that a thin person, as compared to a fat person, would enjoy physical activity and be coordinated, have higher levels of personal weight and body shape satisfaction, and engage in vigorous physical activity more days per week. Conclusions: Perceived weight controllability may be an important construct to study further, particularly in relationship to health- and weight-related attitudes and behaviors. (Contains 2 tables.)