Purpose: This research was conducted to compare the effects of an obesity control program on knowledge of obesity, diet habit, exercise habits, and weight loss of children in a pediatric and adolescent psychiatric hospital. Methods: A non-equivalent control group non-synchronized design was used for this study. Eighteen patients were participated in the experimental group and seventeen were participated in the control group. For 8 weeks, the experimental group received the interventions for fifty minutes weekly, which were consisted of knowledge of obesity, diet habit, and exercise habits and weight loss, while the control group received the usual care during the same period. The outcome variables were measured before and after the program. Data were analyzed using t-test with SPSS/WIN 18.0. Results: The experimental group showed more significant improvement in knowledge of obesity, diet and exercise habits than the control group, but weight loss was not different between the groups. Conclusion: To be more effective obesity control program, nurses should collaborate with other staffs including doctors and social workers, and consistently educate the families of the patients.