Background: This study examined the relationship between actual body weight and self-perceived weight, and how perception of one's weight affects weight management behaviors among US adolescents. Methods: Adolescents ages 16-19 years with objectively-measured weight and height and self-reported perception of weight, weight-loss efforts, and health-related behaviors (N = 642) from the 2009-2010 National Health and Nutritional Examination Survey (NHANES) were included. Sociodemographic variables, body mass index percentile, weight perception, weight-loss efforts, and health-related behaviors were examined using Wald chi-square, Student's t test, analysis of variance, and logistic regression. Results: Approximately 15% were overweight, and 20% were obese; 26% inaccurately perceived their weight. Ethnic minority groups displayed higher rates of overweight and obesity. Overweight adolescents had a higher rate of inaccurate weight perception than obese adolescents. More girls correctly perceived their weight status than boys. Nearly 25% had tried to lose weight during the past year. Among overweight and obese adolescents, accurate weight perception was significantly and positively related to weight-loss efforts after controlling for sociodemographic variables and actual weight. Conclusions: Accurate body weight perception is a significant factor in adolescents' weight-loss efforts. Targeting counseling for body weight perception and weight management toward boys and overweight adolescents may impact obesity in this age group.