Introduction: Non-alcoholic fatty liver disease is defined as the accumulation of fat in the liver in the absence of excessive alcohol consumption or other known pathologies and is a spectrum of disease ranging from steatosis (fat infiltration into the liver) to steatohepatitis. Non-alcoholic steatohepatitis is a more severe form of Non-alcoholic fatty liver disease which is characterised by steatosis, lobular inflammation, ballooning, and fibrosis in liver biopsies. In this study, we aimed to investigate any possible relationship between the ABO/Rh blood group system and Non-alcoholic fatty liver disease / Non-alcoholic steatohepatitis, in Turkey. Materials and methods: A total of 179 patients with hepatosteatosis from Kayseri Training and Research Hospital between the years 2002-2012 were included in the study. The distributions of blood groups of the patients with Non-alcoholic fatty liver disease were compared with the distribution of blood groups of 17.314 healthy donors. The patients were examined for any association between ABO/Rh blood groups and Non-alcoholic fatty liver disease / Non-alcoholic steatohepatitis, and also for an association between ABO/Rh blood groups and grading. Results: Group AB was found to be higher in patients with Non-alcoholic fatty liver disease compared to the control group (p=0.04). The percentage of patients with steatohepatitis was significantly higher in group AB than non-AB blood group (p=0.024). The percentage of patients with steatohepatitis was significantly higher in group grade 3 Non-alcoholic fatty liver disease patients than other two -grade 1 and grade 2 Non-alcoholic fatty liver disease - groups (< 0.001). Conclusion: To our knowledge, this is the first analysis in the literature that investigates the association between the ABO blood groups and Non-alcoholic fatty liver disease / Non-alcoholic steatohepatitis. This epidemiological study can not explain the mechanism behind the blood group effect but may be a light for future studies.