Non-alcoholic fatty liver disease (NAFLD) is currently the most frequently occurring liver disorder in the world. However, a specific drug for the treatment of patients with NAFLD is not available. Therefore, the discovery of novel compounds for the treatment of NAFLD and elucidation of the underlying mechanisms of therapeutic drugs that can be used to treat this disease are urgently needed. 1,2,3,4,6 penta-O-galloyl-β-d-glucose (PGG) is known to exert anti-inflammatory, antidiabetic, and hepatoprotective effects. However, little is known about the therapeutic potential of PGG in NAFLD. In this study, we investigated the effects of PGG on a high-fat diet (HFD)-induced mouse model of NAFLD. PGG was co-administered along with an HFD to C57BL/6 mice. After eight weeks of treatment, serum biochemistry, liver steatosis, and lipid metabolism-related genes were examined. The results showed that PGG treatment significantly reduced HFD-induced gain in body weight, liver steatosis, and leukocyte infiltration in a dose-dependent manner. Furthermore, PGG treatment markedly reduced serum triglyceride and glucose levels in HFD mice. Moreover, alterations in the mRNA expression of genes involved in lipid metabolism, including Hmgcr, Acc1, Abca1, Mttp, and Cd36, observed in the livers of HFD-treated mice were significantly reversed by PGG treatment. PGG significantly reduced HFD-induced protein expression of CD36, which is associated with fatty acid uptake, insulin resistance, hyperinsulinemia, and increased hepatic steatosis, in the liver of HFD mice. These results suggest that PGG inhibits HFD-induced hepatic steatosis and reverses HFD-induced alterations of gene expression in lipid metabolism. PGG has been shown to be well tolerated; therefore, it has potential uses in NAFLD treatment.