OBJECTIVE. We conducted a proof-of-concept, randomized, controlled trial to investigate the effects of a supervised exercise therapy intervention on psychopathologic outcomes in obese adolescents. METHODS. The participant sample consisted of 81 adolescents (age: 11-16 years) who had been referred to a children's hospital for evaluation of obesity or who responded to a community advertisement. Participants were assigned randomly to exercise therapy, an equal-contact exercise placebo intervention, or usual care. Intervention participants attended 3 one-on-one sessions per week for 8 weeks and then completed a home program for another 6 weeks. Outcomes included self-perceptions (self-esteem), depression, affect, physical activity, aerobic fitness, and BMI. RESULTS. A total of 18 of 81 participants were categorized as morbidly obese (BMI SD score: > 3.5; adult equivalent BMI: >= 40). At baseline, 30.3% of participants had a Children's Depression Inventory score of >= 13, and 27% reported recent suicidal ideation. Repeated-measures mixed analysis of covariance (controlling for baseline scores) revealed significant changes in physical self-worth, associated measures of self-esteem, and physical activity over time, consistently favoring exercise therapy. There were no significant changes in BMI. CONCLUSIONS. Findings confirmed psychopathologic conditions as a serious health concern in obese and morbidly obese adolescents. Our study is the first randomized, controlled trial to demonstrate that a brief supervised exercise therapy intervention has the potential to improve psychopathologic outcomes significantly and to increase physical activity in obese adolescents, relative to usual care.