Isocyanic acid, as a reactive metabolite synthesized by the enzyme LACC1, can carbamoylate the ε-amino group of lysine residues in proteins. However, the role of isocyanic acid in inflammatory response remains elusive. Herein, we reveal that lipopolysaccharide stimulation increases LACC1-dependent isocyanic acid production, which attenuates inflammation by limiting the NLRP3 inflammasome activation in macrophages primed with lipopolysaccharide for 8 hours. Mechanistically, isocyanic acid directly carbamoylates NLRP3 at lysine-593 to disrupt NLRP3-NEK7 interaction, a key step in assembly of active NLRP3 inflammasome. Abrogation of isocyanic acid biosynthesis by LACC1/Lacc1 knockout or expression of K593 carbamoylation (K593ca)-deficient NLRP3 mutant promotes macrophagic inflammatory response in vitro. Furthermore, Lacc1-/- mice and mice harboring K593ca-deficient NLRP3 mutation manifest exacerbated inflammatory response in vivo. Hence, our findings identify isocyanic acid as an endogenous immunoregulatory metabolite that limits NLRP3-driven inflammation and provide valuable insights into the regulation of NLRP3 inflammasome activation, governed by metabolites.