OBJECTIVE: Rheumatoid arthritis (RA) is a chronic inflammatory disease, mainly involving joints and bones. Sauchinone is an anti-inflammatory agent isolated from Saururus chinensis, which was used in oriental medicine. The aim of this study was to evaluate the therapeutic effect of sauchinone on inflammatory arthritis and underlying mechanism of anti-arthritic effect. METHODS: Mice with collagen induced arthritis (CIA) was intraperitoneally injected with sauchinone (20 mg/kg) or vehicle. The clinical and histological evaluations were performed with arthritis scoring and hematoxylin-eosin staining, respectively. CD4+ interleukin (IL) 17+ T cells were determined under Th17 skewing condition treated with sauchinone. To evaluate the effect of sauchinone on osteoclastogenesis, mice bone marrow macrophages (BMMs) and human peripheral blood mononuclear cells (PBMCs) were cultured with macrophage-colony stimulating factor and receptor activator of nuclear factor-κB ligand in the absence or presence of sauchinone. RESULTS: Sauchinone significantly attenuated the inflammatory arthritis in CIA mice both clinically and histologically. The proportion of Th17 cells were decreased with treatment with sauchinone in vivo and in vitro. The expressions of Th17 cell markers (IL-17 and retinoic acid receptor-related orphan receptor gamma t) and B cell markers (activation-induced cytidine deaminase) were downregulated in the presence of sauchinone. Sauchinone also suppressed the formation of tartrate-resistant acid phosphatase positive cells from mice BMMs and human PBMCs, and the expression of osteoclastogenic markers. CONCLUSION: Sauchinone alleviates inflammatory arthritis in mice through inhibition of Th17 differentiation and osteoclastogenesis. Sauchinone, one of traditional herbal medicine, could be a therapeutic candidate for the treatment of RA.