CONTEXT: Childhood obesity is rampantly increasing throughout the world and needs to be detected and treated early to prevent non-communicable diseases like diabetes, hypertension and cardiovascular diseases in adulthood. AIMS, SETTING AND DESIGN: This study assessed the prevalence of overweight and obesity in an urban school and determined the factors contributing, using a cross sectional study design. METHODS AND MATERIAL: 1110 children and adolescents aged 6-17yrs took part in the study. The primary students were interviewed by the researcher and middle and high school students completed a questionnaire regarding frequency of meals, snacking, fruits and vegetables intake, time spent watching television/outdoors and family history of obesity. Their heights and weights were recorded according to World Health Organization standards. They were classified into 4 groups-Underweight (BMI less than 18.5kg/m(2)), Normal (BMI 18.5-22.9 kg/m (2)), Overweight (BMI 23-24.9kg/m(2)) and Obese (BMI of 25kg/m(2) and above). Statistical analysis was done based on percentages and proportions. RESULTS: Overall prevalence of overweight and obesity was 6.48%. It was 7.05% among girls and 5.95% among boys. Prevalence of overweight and obesity was 17. 1% higher in children who participated in physical activity less than once in two weeks (P<0.01) and in those whose fathers (P<0.01) and mothers (P<0.001) were overweight or obese. CONCLUSIONS: Any form of physical activity must be encouraged. The role of sports should be emphasized, with compulsory hours of sports in school curriculum. All families with overweight or obese children must be educated on healthy food habits and lifestyle.