This study investigated the preventive effects of a 40% ethanol extract of Hsian-tsao (40EEHT) on obesity in high-fat diet (HFD)-induced obese rats. Male Wistar rats were administered 0, 100, 200, or 500 mg/kg of 40EEHT, resulting in reduced body weight, total body fat, and hepatic tissue weight after 8 weeks. 40EEHT also decreased adipocyte size, improved lipid profiles, alleviated oxidative stress, and enhanced hepatic antioxidant enzyme activities. Additionally, it regulated fatty acid metabolism by reducing lipogenesis and increasing lipolysis and β-oxidation, suggesting its potential as an anti-obesity dietary supplement.