Background: Prevalence of overweight and obesity has increased for the past few decades. World Health Organization refers obesity as a global epidemic. There is a need to assess the prevalence and to find the factors responsible, so as to implement timely interventions. Aims: To assess the prevalence of overweight and obesity among school going children and the factors responsible for the same. Method: The study was conducted in children studying at a private school in Bangalore aged 12-15years. Obesity was assessed using International Obesity Task Force criteria based on the body mass index. Pretested and semi structured questionnaire was used to collect the data on physical activity, eating habits and leisure time activity. Results: The overall prevalence of overweight was 10% and obesity was 5% among 761 adolescents studied. The prevalence of overweight and obesity was 11% and 4% among boys and 9% and 5% among girls respectively. Factors like junk food, chocolate eating, physical inactivity and time spent in watching television and computer gaming were directly related to overweight and obesity. Conclusion: Overweight and obesity are multifactorial and needs a multi pronged interventions at the earliest for control and prevention.