The IL-36 signaling pathway has recently been identified as a key regulator of intestinal homeostasis and inflammation. However, the role of mutations in the IL-36R signaling pathway in the pathogenesis of inflammatory bowel disease remains unclear. We here identified four Crohn's disease patients with heterozygous missense mutations in the IL-36 receptor antagonist (IL36RN, IL-36RA). Experimental overexpression and functional assays demonstrated that two identified mutations resulted in reduced expression of IL-36RA. In-depth immune profiling of one IL36RN-mutated patient revealed an increased response of PBMCs to IL-36 stimulation and elevated serum levels of IL-36-regulated cytokines. Administration of the IL-36R-blocking antibody spesolimab to this patient resulted in a reduction of intestinal inflammation and alterations in immune cell composition and function. Our findings indicate that pathogenic IL36RN mutations may contribute to the pathogenesis of Crohn's disease in a subset of patients and that inhibiting IL-36 signaling could offer a personalized therapeutic approach for these patients.