In recent years, asymmetric dimethyl arginine (ADMA) has emerged as an early marker and/or mediator of endothelial dysfunction and it has been proved to be a novel, independent risk factor of cardiovascular and metabolic diseases. Our aim in this study was to compare the ADMA concentrations among patients with a history of gestational diabetes mellitus (GDM) with controls. Thirty women with a history of GDM and 40 age-matched and BMI-matched healthy controls were enrolled in this study. ADMA concentrations, fasting blood glucose levels, 75-g oral glucose tolerance test (OGTT) second hour plasma glucose levels, and insulin levels were compared between two groups. The fasting blood glucose levels were also significantly higher in patients with GDM history. Although second hour values of 75-g OGTT were higher in patients with GDM history, the difference between groups was not statistically significant. However, the insulin and homeostatic model assessment insulin resistance levels were statistically significantly higher in patients with a history of GDM. The concentrations of ADMA were found to be statistically higher in patients with a history of GDM (0.45 ± 0.11 vs. 0.31 ± 0.13 μmol/l, respectively; P = 0.01). This study shows that women who had a history of GDM are under risk for cardiovascular diseases, although they seem to be healthy and have normal blood biochemical levels, because of elevated serum ADMA levels. Clinicians should be aware of this increased cardiovascular disease risk among patients with a history of GDM.