We examined the effect of nobiletin (5,6,7,8,3',4'-hexamethoxyflavone) on immune response in ovalbumin (OVA)-immunized mice. Treatment with nobiletin increased OVA-specific IL-4 and IL-10 production. In addition, mice that received nobiletin showed higher levels of OVA-specific IgE, IgG and IgG1 production than did control mice. The antibody response to the thymus-independent antigen 2,4,6-trinitrophenyl-Ficoll was not different in the control and nobiletin groups, suggesting that nobiletin does not directly stimulate antibody production. An in vitro study showed that treatment with nobiletin enhanced the ability of antigen presentation of bone marrow-derived dendritic cells. The in vivo and in vitro results indicate that nobiletin regulates immune function.