Introduction: There is rising concern about the increasing prevalence of adolescent obesity in recent decades and despite many studies conducted to elucidate the biological factors of obesity, there is limited data on the psychological factors of obesity. The aim of this study was to investigate the role of body image dissatisfaction and mental health in prediction of obesity. Materials and Methods: This study has a fundamental purpose and the method of data collection is correlational. In this study, 60 students (30 obese and 30 with normal weight) were selected by purposive sampling among the students of schools in Boukan city and the body image questionnaire and general health questionnaire (GHQ) were used to obtain relevant data. Data were analyzed by logistic regression. Results: Results showed that mental health and body image dissatisfaction negatively and significantly predict obesity. Conclusion: Findings demonstrate that mental health and body image are factors affecting weight gain in adolescent girls, indicating that these variables need to be considered in therapy programs aimed at prevention of obesity.