Kawasaki disease (KD) is primarily the systemic vasculitis of childhood that affects mainly the medium-sized arteries, such as the coronary arteries. KD is the leading cause of acquired heart disease, whereas the incidence of rheumatic fever has declined. The most serious complication is coronary artery involvement. Among the children with KD who developed cardiac complications, pericarditis is a rare complication, with an incidence of 0.07%. We report our experience in a 5.5-year-old child with KD complicated with aneurysm of the left anterior descendant coronary artery and septated pericardial effusion, which has not been reported in the literature. The pericardial effusion disappeared very dramatically with intravenous immunoglobulin (IVIG) therapy. We would like to point out that septated pericardial effusion in cases of KD do not need any further therapy other than IVIG and high-dose acetylsalicylic acid.