Viral infection triggers activation of the transcription factors NF-κB and IRF3, which collaborate to induce the expression of type I interferons (IFNs) and elicit innateantiviralresponse. In this report, we identified Krüppel-likefactor4(KLF4) as a negative regulator of virus-triggered signaling. Overexpression of KLF4 inhibited virus-induced activation of ISRE and IFN-β promoter in various types of cells, while knockdown of KLF4 potentiated viral infection-triggered induction of IFNB1 and downstream genes and attenuated viral replication. In addition, KLF4 was found to be localized in the cytosol and nucleus, and viral infection promoted the translocation of KLF4 from cytosol to nucleus. Upon virus infection, KLF4 was bound to the promoter of IFNB gene and inhibited the recruitment of IRF3 to the IFNB promoter. Our study thus suggests that KLF4negativelyregulatescellularantiviralresponse.