BACKGROUND: Ulcerative colitis (UC) is an inflammatory bowel disease with significant morbidity. Cardamonin is a natural chalcone derivative with considerable anti-inflammatory activity. Herein, the potential protective effect of cardamonin against UC was tested in a rat model. METHODS: Rats were given 10 or 30mg/kg/day of cardamonin orally for 14days before induction of UC. On the 14th day of treatment, UC was induced by intrarectal instillation of 2ml 3% acetic acid. Twenty four h after acetic acid instillation, rats were sacrificed and colons were analyzed by macroscopic and histopathological examination. Colon lipid peroxidation was examined by biochemical evaluation of malondialdehyde (MDA). Myeloperoxidase (MPO), iNOS, NF-κB, TNFα levels were measured by ELISA. Moreover, caspase-3 and COX-2 were assessed by immunohistochemical analysis. RESULTS: Cardamonin at 10 and 30mg/kg decreased the disease activity index and macroscopic damage index scores, and significantly reduced histopathological deterioration. Additionally, cardamonin reduced levels of MPO, iNOS, NF-κB, TNFα and MDA (p<0.05). Immunohistochemistry revealed down-regulation of COX-2 and caspase-3 in groups treated with cardamonin. CONCLUSION: Cardamonin has a protective effect against acetic acid-induced colitis. This effect may be due to reducing inflammation, oxidative stress and apoptosis.