Herbal dietary supplements have attracted more and more attention owing to their relative effectiveness in obesity -related metabolic disorders and diseases. This study investigated the therapeutic effects and underlying mechanisms of Capsosiphon fulvescens (CF) extracts on obesity, their associated metabolic disorders and hepatic steatosis in high-fat diet (HFD)-induced obese mice. Male C57BL/6 mice were fed with normal, HFD/Vehicle and HFD/CF (orally 300 mg/kg/day for CF). After 12 weeks, CF blocked HFD-induced body weight, food intake, liver weight, hepatic triglyceride (TG), fat mass (weight of abdominal subcutaneous fat and epididymal adipose tissue) and biochemical parameters (total cohlesterol, glucose, TG, creatinine, high-density lipoproteins cholesterol and low-density lipoprotein cholesterol) of serum. CF also had improved serum levels of adiponectin, leptin and insulin-like growth factor-1 in HFD/CF mice. Moreover, CF ameliorated the hepatic steatosis-reducing size of white adipose tissue. These results indicate that CF have anti-obesity effects and are effective for reducing metabolic risk and hepatic steatosis.