Lupeol is a lupane-type triterpene isolated from Sorbus commixta, an oriental medicine used to treat arthritis and inflammatory diseases. However, the antiosteoporotic effects of S. commixta or any of its constituents have not been studied yet. In the present study, we have examined the effect of lupeol (a major active triterpenoid isolated from S. commixta) on osteoclastogenesis and sought to elucidate its underlying molecular mechanisms. We evaluated whether lupeol antagonized osteoclast differentiation and bone resorption. Lupeol markedly inhibited osteoclast differentiation and bone resorption activity through its effects on MAP kinases and transcription factors (NF-κB, NFATc1, and c-Fos) downstream of the osteoclast differentiation factor receptor RANK. Furthermore, in vivo efficacy of lupeol was confirmed by using an animal model of hypercalcemic mediated bone loss. Taken together, lupeol showed strong inhibitory effects on osteoclastogenesis. Supplementation with S. commixta and lupeol could be beneficial for bone health or osteoclast-related diseases such as osteoporosis, Paget's disease, osteolysis associated with periodontal disease, and multiple myeloma.