Obesity is caused by unbalance of energy intake and expenditure, which results in extra accumulation of adipose tissue. Obesity is directly related to metabolic diseases such as diabetes, hyperlipidemia, fatty liver and so on. To investigate the anti-obesity effects of Scutellariae Radix, 70% EtOH extract and water extract of it were tested by in vitro and in vivo studies of fat accumulation. 3T3-L1 preadipocyte cell line was used in a in vitro study of fat accumulation. After 3T3-L1 cells were induced to differentiate into adipocytes, S. radix extract were added and fat accumulation was measured by oil red O staining. In vivo study showed that weight and epididymal/ retro-peritoneal adipose tissues were significantly reduced in mice fed Scutellariae Radix extract compared with control group. Especially, mice fed Scutellariae Radix extract showed reduced serum triglyceride and glucose levels. When adipose tissues were analyzed by microscope, mean adipocyte size was significantly reduced in Scutellariae Radix extract-fed mice. Therefore, this study showed inhibitory effects of Scutellariae Radix on in vitro and in vivo fat accumulation.