Non-alcoholic fatty liver disease (NAFLD) is one of the major chronic liver diseases that endanger human health. It is characterized by hepatic steatosis and absence of other causes of hepatic fat accumulation, such as alcohol abuse. The incidence of NAFLD is increasing year by year. However, the pathogenesis is still undefined. Porphyromonas gingivalis is a major periodontal pathogen of various periodontal disease. Apart from affecting periodontal health, Porphyromonas gingivalis is also related to the incidence of many systemic diseases. In recent years, Porphyromonas gingivalis is considered to be a risk factor of NAFLD. In this paper, the relationship between NAFLD and Porphyromonas gingivalis, as well as the possible pathogenesis are discussed.