This study was conducted to investigate whether regular dietary intake of L-arginine could affect the occurrence of metabolic syndrome (MetS). Eligible adult men and women (n=1,237), who participated in the Tehran Lipid and Glucose Study, were followed for a median of 6.3 years. Dietary intakes of L-arginine and serum nitrate and nitrite (NOx) concentration were assessed at baseline (2006~2008), and demographics, anthropometrics, and biochemical variables were evaluated at baseline and follow-up examinations. The occurrence of MetS was assessed in relation to total L-arginine, intakes of L-arginine from animal and plant sources, with adjustment of potential confounding variables. Participants who had higher intake of L-arginine also had higher serum NOx at baseline (35.0 vs. 30.5 μmol/L, P<0.05). After 6 years of follow-up, higher intakes of L-arginine from animal sources were accompanied with increased risk of MetS [odd ratios (OR)=1.49, 95% confidence interval (95% CI)=1.02~2.18]. Compared to the lowest, the highest intakes of L-arginine from plant sources were related to significantly reduced risk of MetS (OR=0.58, 95% CI=0.32~0.99). In conclusion, our findings suggest a potentially protective effect of plant derived L-arginine intakes against development of MetS and its phenotypes; moreover, higher intakes of L-arginine from animal sources could be a dietary risk factor for development of metabolic disorders.