Acute scrotum is a rare complication of acute Kawasaki disease (KD), less well recognized than other disease manifestations. We describe the cases of two patients, aged 59 months and 19 months, with hydrocele testis in the acute phase of KD. Scrotal ultrasound and trans-illumination were used in the diagnosis of hydrocele testis. One patient underwent eventual surgical intervention. We reviewed the literature for a better understanding of the pathogenesis of scrotal symptoms in acute KD and investigated the clinical importance of hydrocele testis. Careful further clinical observation may elucidate the true incidence of this extracardiac symptoms, thereby clarifying the diagnostic value of this possible complication in acute KD.