The NLRP3 inflammasome plays a critical role in innate immunity and inflammatory diseases. NIMA-related kinase 7 (NEK7) is essential for inflammasome activation, and its interaction with NLRP3 is enhanced by K+ efflux. However, the mechanism by which K+ efflux promotes this interaction remains unknown. Here, we show that NEK7 is rapidly phosphorylated at threonine-190/191 by JNK1 downstream of K+ efflux and gasdermin D (GSDMD) after NLRP3 activation. NEK7 phosphorylation enhances the binding between NEK7 and NLRP3, which further promotes inflammasome assembly and activation. Mutant mice and macrophages in which Thr190 and Thr191 of Nek7 were replaced by valine exhibited impaired NEK7 phosphorylation, NLRP3 inflammasome activation, and IL-1β secretion. Thus, NEK7 phosphorylation is an important event that acts downstream of K+ efflux and GSDMD to further enhance NLRP3 inflammasome activation.