An aqueous extract of Comus kousa Burg. leaves (ACK) that contained high amount of polyphenols showed significant antioxidant activity against diphenylpicrylhydrazyl (DPPH) radicals and TNF-$alpha$-generated reactive oxygen species. ACK at concentrations of 10 and $50{mu}g/mL$ significantly inhibited TNF-$alpha$-induced adhesion of U937 pre-monocytic cells to HT-29 colon epithelial cells in a concentration-dependent manner. The reduced adhesion by ACK correlated with the suppressed expressions of monocyte chemoattractant protein (MCP)-1 and interleukin (IL)-8, the major inflammatory bowel disease (IBD)-associated chemokines. Moreover, ACK significantly suppressed TNF-$alpha$-induced translocation of redox-sensitive nuclear factor (NF)-${kappa}B$ as well as degradation of cytosolic $I-{kappa}B{alpha}$. The effective concentrations of ACK were much lower than that of 5-aminosalicylic acid (3.06 mg/mL), which is an active metabolite of sulfasalazine, a well-known drug used in the treatment of IBD. The results indicate that ACK may provide a potential benefit for the prevention and treatment of inflammatory diseases such as IBD.