NLRP3 nucleates the inflammasome, a protein complex responsible for cleavage of prointerleukin-1β (IL-1β) to its active form. Mutations in the NLRP3 gene cause the autoinflammatory disease spectrum cryopyrin-associated periodic syndromes (CAPS). The central role of IL-1β in CAPS is supported by the response to IL-1-targeted therapy. We developed two Nlrp3 mutant knockin mouse strains to model CAPS to examine the role of other inflammatory mediators and adaptive immune responses in an innate immune-driven disease. These mice had systemic inflammation and poor growth, similar to some human CAPS patients, and demonstrated early mortality, primarily mediated by myeloid cells. Mating these mutant mice to various gene mutant backgrounds showed that the mouse disease phenotype required an intact inflammasome, was only partially dependent on IL-1β, and was independent of T cells. These data suggest that CAPS are true inflammasome-mediated diseases and provide insight for more common inflammatory disorders.