Increased waist circumference (WC), a surrogate measure for abdominal fat mass, is associated with higher cardiovascular risk not only in adults but also in youth. Identifying healthy dietary patterns that prevent abdominal fat accumulation is of paramount importance for public health. This study investigated the association between adherence to Mediterranean diet guidelines and waist circumference in a representative national sample of young Spaniards (n=2513), aged 10 to 24 years. Dietary data were recorded through a 24-h recall, waist circumference measured by research staff, and adherence to Mediterranean diet guidelines determined with the 16-item KIDMED questionnaire, based on the principles sustaining Mediterranean dietary patterns. A questionnaire provided physical activity and demographic data. Higher KIDMED scoring was significantly associated with higher leisure time physical activity levels and higher maternal education. Multiple regression analysis showed that the KIDMED score was also inversely associated with age- and height-standardized residuals of waist circumference and with waist-to-height ratio (p=0.001). After multivariate adjustment, a 5-point increase in KIDMED was associated with a mean decline of 1.54 cm in sex-, age- and height-adjusted WC. These results suggest that following Mediterranean dietary principles may be important in reducing the risk of high waist circumference in young people.