It is known that women with prior history of gestational diabetes mellitus (pGDM) feature obesity, insulin resistance and endothelial dysfunction which cause premature atherosclerosis. Transforming growth factor-beta 1 (TGF-beta1) is a key cytokine in obesity and insulin resistance and also play important roles in the development of atherosclerosis. This study was conducted to demonstrate the serum TGF-beta1 levels of people with pGDM. Thirty women with pGDM, 20 women with type 2 diabetes mellitus (T2DM) and 20 healthy women were enrolled. Serum TGF-beta1 levels of people with pGDM were found to be significantly higher than healthy controls and significantly lower than women with T2DM. TGF-beta1 levels were found to be correlated with postprandial glucose and age and inversely correlated with body mass index (BMI) and waist circumference. On multiple regression analysis postprandial glucose level, age and BMI were determined as the most important factors affecting TGF-beta1 levels. This study demonstrates elevated TGF-beta1 levels in pGDM. The inflammatory response to hyperglycemia and insulin resistance could be the major factors for the increased expression of TGF-beta1.