The protein tyrosine kinase Src regulates the synthesis of TLR3-mediated IFN-β via the TBK1–IFN regulatory factor 3 axis. However, the molecular mechanisms regulating Src activity in TLR3 signaling remain unclear. In this study, we report that GSK3β regulates Src phosphorylation via TNFR-associated factor 2 (TRAF2)–mediated Src ubiquitination. GSK3β deficiency in mouse embryonic fibroblasts significantly reduces polyinosinic: polycytidylic acid–induced IFN-β and IFN-stimulated gene expression, which is caused by diminished phosphorylation of Src at tyrosine 416. Src undergoes polyinosinic: polycytidylic acid–dependent lysine 63 chain ubiquitination, and TRAF2 is a direct E3 ligase for Src. Our study reveals novel mechanisms underlying TLR3-mediated antiviral responses mediated via the GSK3β–TRAF2–Src axis.