Abstract: Physical activity has been investigated among Asian populations as a factor that influences the clustering of cardiovascular risk factors. However, the magnitude of these associations has not been well studied among adolescents, particularly in Middle East countries. This study aimed to investigate associations between physical activity level, metabolic abnormalities and body composition among adolescent girls in Iran. Socio-demographic and physical activity information were assessed using self-administered questionnaire in 538 adolescent girls aged 15-18 years from Mashhad high schools. Anthropometric, blood pressure and biochemical assessment were performed. Bioelectrical Impedance Analyses was applied to measure total and regional fat mass. The prevalence of overweight, obesity and metabolic syndrome was 14.6, 3.4 and 6.5% respectively. Subjects with lower levels of physical activity had higher anthropometric indices, fat mass, fat free mass and metabolic abnormalities especially systolic blood pressure. There were inverse correlations between physical activity with hypertension, dyslipidemia and body composition parameters. Physical activity was negatively associated with weight (%R = 2.8 B = -0.168, p<0.0001), systolic blood pressure (%R = 3.9 B = -0.158, p<0.0001), triglyceride concentration (%R = 3.9 B = -0.106, p<0.018) and fat free mass (%R = 4.2 B = -0.205, p<0.0001) after adjusting for age and socioeconomic status of family. Subjects with metabolic syndrome had lower levels of physical activity (1.37 vs 1.39, p<0.05) and higher basal metabolic rate (1426 kcal vs 1360, p<0.0001). To avoid increasing risk of cardiovascular diseases, programs to promote greater physical activity should be implemented.