The purpose of this study was to investigate the anti-obesity effects of crude saponin (CS) in Korean red ginseng (KRG) on rats fed a high fat (HF) diet. Methods: Male Sprague-Dawley (SD) rats were divided into a normal diet group and a high-fat (HF) diet group. The HF diet group became obese from being fed a HF diet over five weeks. The normal diet group were fed a normal diet. Each CS group of the normal diet group and HF diet group was administered CS (200 mg/kg, i.p.) for three weeks, the control group of both types was administered normal saline (1ml/kg, i.p.) instead of CS. Each group had 5 rats. Results: After administration of CS, the body weight, food consumption, adipose tissues, and expression of appetite peptides such as leptin and neuropeptide-Y (NPY) were investigated in the HF diet group as well as the normal diet group. Administration of CS reduced body weight, food intake, and fat content in the HF and normal diet groups. After CS administration, NPY expression and leptin were lower in the HF diet group. Conclusions: Our results suggest that CS may be useful in the treatment of obesity, especially of type qixu (氣虛).