Kawasaki disease (KD) is a systemic febrile vasculitis particular coronary artery involvement. Eosinophilia has been found in our and other studies in KD. This study further investigates whether eosinophil-related T helper 2 (Th2) cytokines or the activation marker (eosinophil cationic protein - ECP) is involved in KD with coronary artery lesions (CAL). A total of 95 KD patients were enrolled for this study. Plasma samples were subjected to the measurement of interleukin (IL)-4, IL-5, and eotaxin by Luminex-Bedalyte multiplex beadmates system and to the measurement of ECP by fluoroimmunoassay. Patients with KD had higher eosinophils than controls. Eosinophil-related mediators: IL-4, IL-5, eotaxin, and ECP levels were also higher in KD patients than controls before intravenous immunoglobulin (IVIG) treatment. After IVIG treatment, ECP decreased but IL-4, IL-5, and eotaxin increased significantly. The higher the IL-5 and eosinophil levels after IVIG treatment, the lower rate of CAL was found. Changes of eosinophils after IVIG treatment were positively correlated to changes of IL-5 levels but not ECP levels. An increase of eosinophils and IL-5, but not ECP levels after IVIG treatment, was inversely correlated with CAL formation in KD.