Objectives : The aim of this study was to investigate the effects of Gamisaenggan-tang on high fat diet induced nonalcoholic fatty liver disease. Methods: Rats were randomly divided into four groups. The Normal group was fed a solid diet containing 10% fat. The Gamisaenggan-tang (GS) group was fed a solid diet containing 10% fat and Gamisaenggan-tang (90mg/100g body weight). The Control group was fed a solid diet containing 60% fat. The HFD-Gamisaenggan-tang (HFD-GS) group was fed a solid diet containing 60% fat and Gamisaenggan-tang (90mg/100g body weight). Six weeks later, rats body weight, liver weight, serum ALT, GGT, ALP levels were measured. Histological findings (Oil red O staining), hepatic triglyceride, TNF-${alpha}$, and TGF-${eta}$ levels in the liver tissue were studied. Results: Average body weight of the HFD-GS group was significantly less than that of the Control group. There were no significant liver weight differences among each group. The GGT levels of the HFD-GS group were significantly less than those of the Control group. However, there were no significant differences in the ALT or ALP levels among the groups. TNF-${alpha}$ protein production assessed by western blot analysis was reduced by Gamisaenggan-tang. Greater fat accumulation was observed in the liver tissue of the Control group than in the HFD-GS group, which means the Gamisaenggan-tang has an inhibitory effect on the accumulation of fat in the liver. Conclusion : The results suggest that Gamisaenggan-tang can be potential candidate for the treatment of nonalcoholic fatty liver disease in clinics.