BACKGROUND: Kawasaki disease (KD) is acute and self-limited vasculitis caused by unknown origin, and the critical complication in KD patients is coronary artery lesions (CALs). The endothelial glycocalyx is a network of membranes luminally covering the endothelium. This study aimed to evaluate the clinical utility of serum glycocalyx components as biomarkers of predicting the onset CALs in KD. METHODS: Seventy subjects with complete type KD, 18 subjects as febrile control (FC), and 15 subjects as afebrile controls (AC) were enrolled. Medical, demographic, echocardiography, and laboratory data from the medical records were retrospectively analyzed. Serum syndecan-1 and hyaluronan levels prior to intravenous immunoglobulin (IVIG) therapy were measured at the acute phase, immediately after IVIG, the subacute phase, and the time of discharge at the convalescent phase. RESULTS: Serum syndecan-1 and hyaluronan levels were higher in the KD group than in the AC and FC groups at all three phases. Further, these levels were compared between KD patients with and without the development of CALs. Serum syndecan-1 and hyaluronan levels at the acute phase were significantly elevated in KD patients with the CALs than in those without CALs. Serum hyaluronan, not syndecan-1, was determined as the most contributory parameter to predict CALs by a multiple logistic analysis. CONCLUSIONS: Circulating syndecan-1 and hyaluronan can be useful biomarkers to predict the development of CALs in KD.