Celecoxib is a specific inhibitor of cyclooxygenase 2 (COX2). While it has been used for the treatment of chronic inflammatory conditions, including rheumatoid arthritis, its detailed anti-inflammatory mechanism has not been clarified. Here, we found that Celecoxib potently inhibited TNFalpha-induced transcriptional activity and DNA binding activity of NF-kappaB; however, Celecoxib had no effect on TNFalpha-induced IKK activation and degradation of IkappaBalpha and IkappaBbeta, suggesting that it inhibited NF-kappaB activation via suppressing downstream of IKK activation and IkappaBs degradation. Interestingly, it was also found that Celecoxib abrogated TNFalpha-induced nuclear accumulation of the NF-kappaB p65 subunit. As a result, TNFalpha-induced expression of inflammatory cytokines, CXCL1/KC and CCL2/MCP-1, was clearly inhibited by Celecoxib. On the other hand, Celecoxib had no effect on the TNFalpha-induced nuclear translocation of c-jun and activation of ERK, JNK, p38 and Akt. Taken together, these data indicate that Celecoxib specifically inhibits TNFalpha-induced NF-kappaB activation at the level of its nuclear translocation. This negative regulation of NF-kappaB activation by Celecoxib might be an important mechanism leading to its anti-inflammatory activity.