Although T cell-mediated immune response to influenza virus has been extensively studied, little information is available on direct interaction between influenza virus and T cells that pertains to severe diseases in humans and animals. To address these issues, we utilized the BALB/c mouse model combined with primary T cells infected with A/WSN/33 influenza virus to investigate whether influenza virus has an affinity for T cell in vivo. We observed that small portions of CD4+ T cells and CD8+ T cells in spleen and thymus expressed viral proteins in infected mice. A significant proportion of mouse primary T cells displayed expression of alpha-2,6 sialic acid-linked influenza virus receptor and was directly infected by influenza A virus. These experiments reveal that there exists a population of T cells that is susceptible to influenza A virus infection. Furthermore, we employed human Jurkat T cell to investigate the virus/T cell interaction with particular emphasis on understanding of whether Interleukin-2-inducible T cell kinase (Itk), a Tec family tyrosine kinase that regulates T cell activation, is involved in viral infection of T cell. Interestingly, influenza virus infection resulted in an increased expression of Itk recruited to the plasma membrane and an increased level of PLC-γ1 phosphorylation, suggesting that Itk/PLC-γ1 signaling is activated by the viral infection. We demonstrated that depletion of Itk inhibited the replication of influenza A virus, whereas overexpression of Itk increased viral replication. These results indicate that Itk is required for efficient replication of influenza virus in infected T cells.