Interleukin-17 (IL-17), a member of the IL-17 cytokine family, plays a crucial role in mediating the immune response against extracellular bacteria and fungi in the lung. Although there is increasing evidence that IL-17 is involved in protective immunity against H1 and H3 influenza virus infections, little is known about the role of IL-17 in the highly pathogenic H5N1 influenza virus infection. In this study, we show that H5N1-infected IL-17 knockout (KO) mice exhibit markedly increased weight loss, more pronounced lung immunopathology and significantly reduced survival rates as compared with infected wild-type controls. Moreover, the frequency of B cells in the lung were substantially decreased in IL-17 KO mice after virus infection, which correlated with reduced CXCR5 expression in B cells and decreased CXCL13 production in the lung tissue of IL-17 KO mice. Consistent with this observation, B cells from IL-17 KO mice exhibited a significant reduction in chemokine-mediated migration in culture. Taken together, these findings demonstrate a critical role for IL-17 in mediating the recruitment of B cells to the site of pulmonary influenza virus infection in mice.