We had tested antiobesity effect of 52 traditional herbal formulas in 3T3-L1 adipocyte, and Banhasasim-tang (BHSST) was chosen as one of the effective medications to inhibit triglyceride accumulation. We investigated the antiobesity effect of BHSST on 3T3-L1 adipocytes and high-fat diet- (HFD-) induced obese mice. In addition, we evaluated the acute toxicity of BHSST in Sprague Dawley (SD) rats. Differentiated 3T3-L1 cells were treated with various concentrations of BHSST for 8 days. Accumulated triglyceride level and the expressions of adipogenesis-related genes and proteins were subsequently investigated. To evaluate the single oral toxicity of BHSST, the SD rats of each sex were administered a single dose (5000 mg/kg) of BHSST via oral gavage; the control group received vehicle only. After a single administration, the mortality, clinical signs, gross findings, and body weight were monitored for 15 days. Male C57BL/6J mice were fed HFD for 4 weeks to induce obesity and randomly received 50 mg/kg of Orlistat (n=12, OR), 200 mg/kg of BHSST (n=12, B200), and 1000 mg/kg of BHSST (n=12, B1000) for another 8 weeks. BHSST suppressed the triglyceride contents and lipid accumulation in a dose-dependent manner in 3T3-L1 adipocytes. BHSST also downregulated the adipogenesis-related gene levels and protein expression compared with those in undifferentiated adipocytes. In a single oral dose toxicity study, there was no adverse effect on mortality, clinical signs, body weight changes, and gross findings in the treatment group. HFD-fed mice treated with BHSST showed significantly reduced body weight gain, food efficiency ratio, and white adipose tissue weight. The medial lethal dose (LD50) of BHSST was 5000 mg/kg/day body weight for each sex in the rats. BHSST decreased the body weight gain in HFD-fed obese mice and inhibited triglyceride accumulation via a cascade of multiple factors at the mRNA and protein levels in 3T3-L1 adipocytes.