One of the major epidemiologic public health problems is worldwide metabolic syndrome (MetS). Since the relationship between diet quality and MetS among adolescents in developing countries has not been well understood, the present study aimed to evaluate the association between diet quality, as measured by Healthy Eating Index (HEI-2005) and the prevalence of MetS and its risk factors in a group of Tehranian adolescents. This crosssectional study was conducted on 706 adolescents, aged 10-19 years, within the framework of Tehran Lipid and Glucose Study in 2008-2011. Usual dietary intakes were assessed by valid and reliable semi-quantitative food frequency questionnaire and diet quality score was obtained based on HEI-2005. MetS was determined using the modified de Ferranti definition. There were 706 adolescents, aged 14.8±2.7 years. The overall prevalence of MetS in adolescents was 22.4%. Large waist circumference was the most common component of MetS in both girls and boys. After adjusting for age, sex, energy intake and physical activity, participants who were in the highest quartile of HEI-2005 compared with lowest quartile had lower prevalence of hypertriglyceridemia (OR: 0.62; CI 95%: 0.40-0.96 and P for trend= 0.02), and low serum HDL-C (OR: 0.62; CI 95%: 0.41-0.97 and P for trend= 0.02). No significant difference was observed in odds of MetS, large waist circumference, hyperglycemia and hypertension. Adolescents with dietary pattern more consistent with the HEI-2005, had lower prevalence of hypertriglyceridemia and low serum HDL-C.