The purpose of this study was to investigate anti-obesity and anti-hyperlipidemic effects of extracts from Geranium thunbergii (GT) in high-fat-diet-induced obese rats. Animals were randomly divided into four groups [normal diet, high fat diet, MeOH extract of GT (GTM), and BuOH fraction of GT (GTB)] and GT samples were treated with dose of 100 mg/kg for 8 weeks. It was observed that GTB-treated group significantly reduced body weight gain, food intake, epididymal fat weight, and triglyceride level in serum and liver compared to control group. The rats fed GTB also decreased contents of thiobarbituric acid-reactive substances (TBARS), hydroxyl radical, and xanthin oxidase (XO) increased by high fat diet. Furthermore, the anti-oxidant enzymes such as superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase were increased by GTB treatment. The experimental results indicate that GTB has anti-obesity and anti-hyperlipidemic effects, as well as radical scavenging activity.