Background Dexmedetomidine (DEX) is a novel highly selective α2-adrenoceptor agonist with sedative, analgesic, and anxiolytic effects. Although it has not been approved by the US FDA for pediatric patients under 18 years old, there are a lot of literatures focusing on its using in pediatric patients with congenital heart diseases. Objective This paper discusses the application of DEX in children with congenital heart diseases in detail. Content The clinical applications of DEX in cardiac surgery include sedative in pediatric intensive care unit，sedation during non-invasive and invasive procedures, as part of multimodal anesthetic regimen, treatment of supraventricular tachyarrhymias and prevention of drug withdrawal. Trend DEX is a safely drug while using in critically ill patients, with advantage of wide dose range and minimal respiratory depression.