Significance Infection of pathogenic microbes induces the body to produce cytokines, which are mediators of inflammation. IL-1β plays central roles in the initiation of inflammatory and immune responses. In this study, we identified MARCH3 protein, which negatively regulates IL-1β–triggered signaling and inflammatory response by mediating K48-linked polyubiquitination of IL-1RI at lysine 409 and its lysosomal degradation. Our findings reveal a mechanism for how IL-1β–triggered inflammatory response is attenuated by down-regulation of IL-1β receptor.