NLRP3 is a key component of the macromolecular signaling complex called the inflammasome that promotes caspase 1-dependent production of IL-1β. The adaptor ASC is necessary for NLRP3-dependent inflammasome function, but it is not known whether ASC is a sufficient partner and whether inflammasome formation occurs in the cytosol or in association with mitochondria is controversial. Here, we show that the mitochondria-associated adaptor molecule, MAVS, is required for optimal NLRP3 inflammasome activity. MAVS mediates recruitment of NLRP3 to mitochondria, promoting production of IL-1β and the pathophysiologic activity of the NLRP3 inflammasome in vivo. Our data support a more complex model of NLRP3 inflammasome activation than previously appreciated, with at least two adapters required for maximal function. Because MAVS is a mitochondria-associated molecule previously considered to be uniquely involved in type 1 interferon production, these findings also reveal unexpected polygamous involvement of PYD/CARD-domain-containing adapters in innate immune signaling events. Display omitted Display omitted ► Inactive NLRP3 is cytosolic and associates with mitochondria upon activation. ► The mitochondrial adaptor MAVS mediates NLRP3 recruitment to mitochondria. ► The N terminus of NLRP3 regulates MAVS association and mitochondrial recruitment. ► MAVS promotes NLRP3-mediated production of mature IL-1β Optimal NLRP3 inflammasome activity requires recruitment to the mitochondria via the adaptor protein MAVS. The MAVS-NLRP3 interaction plays a critical role in the response to infection and tissue damage and in inflammatory disease.