Backgroud: The stem bark of Kalopanax pictus (KP) has been used in traditional medicine to treat rheumatoidal arthritis, neurotic pain and diabetes mellitus in China and Korea. In this study, the mechanism responsible for anti-inflammatory effects of KP was investigated. Methods: We examined the effects of KP on NO production, nitric oxide synthase (iNOS) and HO-1 expression, NF-${kappa}B$, Nrf2 and MAPK activation in mouse peritoneal macrophages. Results: The aqueous extract of KP inhibited LPS-induced NO secretion as well as inducible iNOS expression, without affecting cell viability. KP suppressed LPS-induced NF-${kappa}B$ activation, phosphorylation and degradation of $I{kappa}B-{alpha}$, phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun N-terminal kinase (JNK). Furthermore, KP induced HO-1 expression and Nrf2 nuclear translocation. Conclusion: These results suggest that KP has the inhibitory effects on LPS-induced NO production in macrophages through NF-${kappa}B$ suppression and HO-1 induction.