Context: YKL-40 is an inflammatory biomarker for endothelial dysfunction that may have a role in Kawasaki disease (KD).Objectives: We investigated the association of serum YKL-40 levels with KD and established laboratory parameters for YKL-40 levels and other inflammatory markers.Methods: YKL-40 levels and other inflammatory markers of 23 KD patients, 9 disease control patients and 11 age-matched healthy controls.Results: YKL-40 concentration in the serum of KD patients significantly increased during the acute disease phase compared with those of disease controls and healthy controls.Conclusions: Increased YKL-40 levels may provide a useful inflammatory marker for patients with KD.