Abstract Background: The components of the metabolic syndrome are closely related with endothelial dysfunction, which is a pathophysiological issue of cardiovascular diseases. Non-alcoholic fatty liver disease (NAFLD) is considered as one of the components of the metabolic syndrome. The aim of this study was to evaluate the endothelial-dependent dilatation (EDD) and endothelial-independent dilatation (EID) of the brachial artery in NAFLD. Methods: Fifteen non-alcoholic steatohepatitis (NASH), 17 patients with simple steatosis and 16 healthy subjects formed the study group. Non-alcoholic fatty liver disease group was composed of patients admitted to the gastroenterology outpatient clinic because of increased liver enzymes. Endothelial functions of the brachial artery were evaluated by vascular ultrasound. EDD was assessed by establishing reactive hyperaemia, and EID was determined by using sublingual nitrate. Results: No statistical difference for the basal diameter of brachial artery was found between the groups (P = 0.49). The values for EDD and EID were significantly different across all three groups (P < 0.0001 and P < 0.0001, respectively). EDD and EID were significantly lower in NASH compared with simple steatosis (P = 0.01 and P < 0.01, respectively). However, there was no statistical significance for EDD and EID in simple steatosis groups compared with controls (P = 0.58 and P = 0.98, respectively). Conclusions: Our study showed that patients with NASH had significantly worse endothelial dysfunction compared with patients with simple steatosis and healthy subjects. The treatment strategies with ameliorative effects for endothelial dysfunction might be effective for delaying the development of cardiovascular complications in NAFLD.