ABSTRACT Objective Analyzing the prevalence of metabolic syndrome and its association with adolescent diet quality. Methods Cross-sectional research with 327 adolescents from public and private high schools of Teresina, Piauí. Socioeconomic, anthropometric, and food consumption data were analyzed to obtain the Brazilian Healthy Eating Index-Revised. Moreover, data related to metabolic syndrome (blood glucose, blood pressure, waist circumference, triglycerides, and high-density lipoprotein cholesterol) were also analyzed. Continuous variables were described by means, standard deviations, and 95% confi dence intervals. To verify the association between dependent and explanatory variables, we calculated the adjusted odds ratio. The level of signifi cance was set at p<0.05. Results The prevalence of metabolic syndrome was 3.3%, with low high-density lipoprotein cholesterol concentration being the most frequent alteration (50.5%). The mean score on the Brazilian Healthy Eating Index-Revised was 55.4 points. The worst scores were obtained in whole cereals, dark-green and orange vegetables, oils, milk and dairy products, and whole fruits. In contrast, total cereals, meat, eggs, and legumes had scores close to the maximum stipulated. The lowest tertile of dark-green, orange, and leguminous vegetables showed risk for low high-density lipoprotein cholesterol, and the second tertile was protective against high blood glucose levels. As for the milk group, its lower intake increased the chances for high triglyceride and blood pressure levels. Conclusion Despite the low prevalence of metabolic syndrome, there were significant alterations in its components,associated with less consumption of important Brazilian Healthy Eating Index-Revised items.