Abstract Purpose To assess the role of the interleukin (IL)-17 A/IL-17 receptor A (IL-17RA) in Kawasaki disease (KD)-related coronary arteritis (CA). Methods In human study, the plasma levels of IL-17 A and coronary arteries were concurrently examined in acute KD patients. In vitro responses of human coronary endothelial cells to plasma stimulation were investigated with and without IL-17RA neutralization. A murine model of Lactobacillus casei cell-wall extract (LCWE)-induced CA using wild-type Balb/c and Il17ra-deficient mice were also inspected. Results The plasma levels of IL-17 A were significantly higher in KD patients before intravenous immunoglobulin therapy, especially in those with coronary artery lesion. The pre-IVIG IL-17 A levels positively correlated with maximal z scores of coronary diameters and plasma-induced endothelial mRNA levels of chemokine (C-X-C motif) ligand-1, IL-8, and IL-17RA. IL-17RA blockade significantly reduced such endothelial upregulations of aforementioned three genes and inducible nitric oxide synthase, and neutrophil transmigration. IL-17RA expression was enhanced on peripheral blood mononuclear cells in pre-IVIG KD patients, and in the aortic rings and spleens of the LCWE-stimulated mice. LCWE-induced CA composed of dual-positive Ly6G- and IL-17 A-stained infiltrates. Il17ra-deficient mice showed reduced CA severity with the fewer number of neutrophils and lower early inducible nitric oxide synthase and chemokine (C-X-C motif) ligand-1 mRNA expressions than Il17ra^+/+ littermates, and absent IL-17RA upregulation at aortic roots. Conclusion IL-17 A/IL-17RA axis may play a role in mediating aortic neutrophil chemoattraction, thus contributory to the severity of CA in both humans and mice. These findings may help to develop a new therapeutic strategy toward ameliorating KD-related CA.