Background: Parthenolide (PT), a NF-kB inhibitor, has recently been demonstrated as a promising anticancer agent that promotes apoptosis of cancer cells. We previously showed that PT suppresses tumor growth in a xenograft model of colorectal cancer cells by regulation of Bcl-2 family. Unfortunately, little is known about its role in the process of tumor development in colitis associated colon cancer (CAC). Methods: Therefore, this study was designed to investigate the effects of PT on an experimental murine CAC model. Experimental CAC was induced by azoxymethane (AOM) and dextran sulfate sodium (DSS). Mice were divided into 3 groups: AOM+DSS, AOM+DSS+2mg/kg PT and AOM+DSS+4mg/kg PT. Results: We demonstrated that administration of PT significantly reduced the severity of AOM/DSS-induced CAC as assessed by histological analysis, and resulted in downregulation of phospho-NF-κB p65 expression by the blockade of phosphorylation and subsequent degradation of IκB-a. Administration of PT ameliorated the carcinogenesis through the downregulation of antiapoptotic protein Bcl-2 and Bcl-xL mediated by inhibition of NF-kB activation. Moreover, apoptosis and caspase-3 expression also increased markedly in PT administration group. Conclusions: These findings demonstrate that PT downregulates NF-kB resulting in initiation of apoptosis and eventual suppression of CAC development, suggesting that PT exerts beneficial effects in experimental CAC and could therefore be a potential chemopreventive and therapeutic agent of CAC.