Guggulsterone is a plant sterol that is used to treat hyperlipidemia, arthritis, and obesity. Although its anti-inflammatory and anti-hyperlipidemic effects have been well documented, the effect of guggulsterone on fibroblast-like synoviocytes (FLS) has not yet been reported. Therefore, in this study, the effect of guggulsterone on interleukin (IL)-1β-induced inflammatory responses in the FLS of rheumatic patients was investigated. Treatment of FLS with IL-1β induced production of chemokines such as RANTES and ENA-78. In addition, Western blot analysis and gelatin zymography revealed that IL-1β activated matrix metalloproteinase (MMP)-1 and -3 in FLS. However, pre-incubation with guggulsterone completely inhibited the ability of IL-1β to induce the production of chemokines and to activate MMPs. Although the NF-κB binding activity and nuclear p50 and p65 subunit levels, as well as IκBα degradation in the cytoplasm was greater in cells stimulated with IL-1β than in unstimulated cells, treatment with guggulsterone abolished all of these increases. Collectively, these results suggest that guggulsterone would be useful as an inhibitor of joint destruction in patients with rheumatoid arthritis.