Nonalcoholic fatty liver disease (NAFLD) is a common cause of chronic liver disease. Non-alcoholic fatty liver disease is a spectrum of simple steatosis that is benign to non-alcoholic steatohepatitis (NASH) associated with fibrosis and inflammation. Genetic factors play an important role in this disease. The PNPLA3 gene (C > G) rs738409 polymorphism has been defined to be associated with increased liver fat content and liver damage in metabolic disorders. In this study, the association of this polymorphism with non-alcoholic fatty liver disease was investigated in the Mazandaran province population. Our study population consisted of 85 patients and 85 controls. Blood samples were collected from patients and DNA were then extracted by boiling method. Genotypes of this polymorphism were determined by PCR-RFLP method. There was a significant relationship between CG genotype and risk of NAFLD (P = 0.012).