AbstractAimAnimals exhibit physiological changes designed to eliminate the perceived danger, provoking similar symptoms of fever. However, a high‐grade fever indicates poor clinical outcomes. Caspase11 (Casp11) is involved in many inflammatory diseases. Whether Casp11 leads to fever remains unclear. In this study, we investigate the role of the preoptic area of the hypothalamus (PO/AH) microglia Casp11 in fever.MethodsWe perform experiments using a rat model of LPS‐induced fever. We measure body temperature and explore the functions of peripheral macrophages and PO/AH microglia in fever signaling by ELISA, immunohistochemistry, immunofluorescence, flow cytometry, macrophage depletion, protein blotting, and RNA‐seq. Then, the effects of macrophages on microglia in a hyperthermic environment are observed in vitro. Finally, adeno‐associated viruses are used to knockdown or overexpress microglia Casp11 in PO/AH to determine the role of Casp11 in fever.ResultsWe find peripheral macrophages and PO/AH microglia play important roles in the process of fever, which is proved by macrophage and microglia depletion. By RNA‐seq analysis, we find Casp11 expression in PO/AH is significantly increased during fever. Co‐culture and conditioned‐culture simulate the induction of microglia Casp11 activation by macrophages in a non‐contact manner. Microglia Casp11 knockdown decreases body temperature, pyrogenic factors, and inflammasome, and vice versa.ConclusionWe report that Casp11 drives fever. Mechanistically, peripheral macrophages transmit immune signals via cytokines to microglia in PO/AH, which activate the Casp11 non‐canonical inflammasome. Our findings identify a novel player, the microglia Casp11, in the control of fever, providing an explanation for the transmission and amplification of fever immune signaling.