Background & Aim: Insulin resistance syndrome, a cluster of metabolic abnormalities, is accompanied by an increased risk of diabetes and cardiovascular diseases. This has become an important problem in urban children due to their increasing levels of obesity. The aim of the present study is to determine the status of metabolic syndrome in obese urban children of Iran. Patients & Method: 535 obese 7 to 11-year-old students of all the primary schools of the 6th district of Tehran were studied according to their waist circumference and International Obesity Task Force(IOTF) criteria. Waist circumference, fasting serum triglyceride, high density lipoprotein(HDL) cholesterol, blood pressure, fasting plasma glucose, and insulin levels were measured. Results: The crude prevalence rate of metabolic syndrome in these children was 20.6%. There was no significant difference between genders. The most common metabolic abnormality was hypertriglyceridemia and the least common one was low HDL levels. All the components of metabolic syndrome except low HDL levels were significantly higher in obese children with metabolic syndrome. Moreover, these children showed distinctly higher insulin levels. Conclusion: The prevalence of metabolic syndrome is high in obese Iranian children. Early intervention in this population who will become our future obese adults is needed not only to increase their life quality but also to decrease the future burden of diabetes and cardiovascular diseases on our society.