Kawasaki syndrome (KS) is an acute febrile vasculitis of childhood. Coronary artery abnormalities (CAA) are a significant problem in KS patients. High dose intravenous immunoglobulin (IVIG) is effective for reducing the occurrence of CAA. Clinical and histopathological findings suggest that vascular endothelial growth factor (VEGF) is involved in CAA. In circulating blood, newly activated platelets are the major source of VEGF, which is released in large amounts in vascular inflammation. The present study analysed 80 KS patients (69 IVIG responders and 11 IVIG non-responders) and evaluated the role of platelet VEGF in KS vasculitis. Serum VEGF and platelet VEGF levels were significantly higher in KS patients than controls (P < 0.001). Platelet VEGF reflected the reactivity of IVIG treatment and was decreased in responders (P < 0.001), but remained increased in non-responders (P = 0.01). Platelet VEGF levels, but not serum VEGF levels, before IVIG were significantly correlated with the maximum CAA z-score (r = 0.524, P = 0.02). Our findings demonstrate that platelet VEGF may reflect the severity of vasculitis related to the pathological development of CAA in KS. Platelet VEGF may be an important feature of KS pathophysiology.