To determine Korean mistletoe lectin (KML-C) functions as a mucosal adjuvant, we monitored its ability to modulate the immune response after intranasal immunization with hemagglutinin (HA) as an antigen. Mucosal and systemic immune responses with KML-C were compared to responses with cholera toxin B subunit (CTB) as an adjuvant. Intranasal co-administration of HA and KML-C in mice resulted in increased anti-HA antibody titers in both vaginal wash and serum. Isotyping analysis revealed that KML-C augmented HA-specific antibody titers of IgG1, IgG2a, and IgG2b isotypes. More than 5-fold of interleukin 2 (IL-2), 3-fold of interferon-${gamma}$ (IFN-${gamma}$), and 4-fold of granulocyte macrophage colony-stimulating factor (GM-CSF) mRNA were detected using real time PCR in splenocytes of mice immunized with HA plus KML-C. Fluorescence activated cell sorting (FACS) analysis indicated that co-administration of KML-C increased the subpopulation of CD3/CD8 double positive T cells (16.4%) than control (10%). Taken together, these data demonstrate that KML-C has the ability to serve as a mucosal adjuvant.