Obesity has become one of the main public health problems. Saussurea lappa (Asteraceae), syn Aucklandia lappa and Saussurea costus, is a well-known herbal medicine that has been used for treating various ailments, such as inflammatory and gastrointestinal diseases. The present study examined the anti-obesity effect of S. lappa extract (SLE) in 3T3-L1 adipocytes and high fat diet (HFD)-induced obese mouse model. SLE significantly inhibited the differentiation from preadipocytes to adipocytes of cultured 3T3-L1 in dose-dependent manner. In addition, SLE significantly decreased the body weight gain and the food efficiency ratio of mice fed HFD during 9 weeks. Further study must be performed for the pharmacological mechanism and safety of SLE as well as the identification of active compound in SLE. Our results revealed that S. lappa suppresses the adipogenesis in cultured cells and the obesity in rodent models. Therefore, S. lappa may be useful toward the development of new potent anti-obesity drugs.