Lithium salt is a widely used glycogen synthase kinase-3β inhibitor and effective drug for the treatment of psychiatric diseases. However, the effects of lithium in innate immune responses, especially in cellular antiviral responses, are unknown. In this study, we show that lithium chloride attenuates LPS-, polyinosinic-polycytidylic acid-, and Sendai virus-induced IFN-β production and IFN regulatory factor 3 activation in macrophages in a glycogen synthase kinase-3β-independent manner. The ability of the lithium to inhibit IFN-β production was confirmed in vivo, as mice treated with lithium chloride exhibited decreased levels of IFN-β upon Sendai virus infection. In vitro kinase assay demonstrates that lithium suppresses TANK-binding kinase 1 kinase activity. Consistently, lithium significantly enhanced the replication of vesicular stomatitis virus in vitro and in vivo. Severe infiltration of monocytes and tissue damage were observed in the lungs of control mice, compared with lithium-treated mice after virus infection. Our findings suggest lithium as an inhibitor of TANK-binding kinase 1 and potential target for the intervention of diseases with uncontrolled IFN-β production. Furthermore, lithium attenuates host defense to virus infection and may cause severely adverse effects in clinical applications.