The innate immune responses are tightly regulated to ensure effective clearance of invading pathogens and avoid excessive inflammation. Ubiquitination and deubiquitination are important post-translational modifications in antiviral immune responses. Here, we discovered deubiquitinase USP47 as a novel negative immune system regulator. Overexpression of USP47 repressed Sendai virus, poly(I:C) and poly(dA:dT)-induced ISRE and IFN-β activation, along with reduced IFNB1 transcription and enhanced viral replication. Knockdown of USP47 expression had the opposite effects. Dual-luciferase and phosphorylation assays showed that USP47 targeted downstream of MAVS and upstream of TBK1. Additional co-immunoprecipitation assays suggested that USP47 interacted with TRAF3 and TRAF6. Importantly, USP47 removed K63-linked polyubiquitin chains from TRAF3 and TRAF6. Hence, we describe a novel modulator of the antiviral innate immune response, USP47, which removes K63-linked polyubiquitins from TRAF3 and TRAF6, leading to reduced type I IFN signaling.