The Fontan operation is a heart operation used to treat complex congenital heart defects like tricuspid atresia, hypoplastic left heart syndrome, pulmonary atresia and single ventricle. A single ventricle is dedicated to pumping oxygenated blood to the systemic circulation and the entire systemic venous return reaches the pulmonary arterial system without the direct influence of a pumping chamber. In the patient with Fontan operation, it is important to achieve adequate pulmonary blood flow and cardiac output in anesthetic management. In this case, a 10-year-old boy (19.6 kg, 114 cm) with cleft palate, cerebral palsy and severe mental retardation, who underwent a Fontan operation when he was 4 years old, was presented for deep sedation. Because he was suffering from eating disorder with cleft palate, the orthodontist and the plastic surgeon planned to insert intraoral orthodontic device before cleft palate repair. But it was impossible to open his mouth for alginate impression procedure. After careful pre-anesthesia evaluation we planned to administer deep sedation with propofol infusion. After Intravenous catheter insertion, we started propofol intravenous infusion with the formula of a loading dose of 1.0 mg/kg followed by an infusion rate of 6.0 mg/kg/hr with syringe pump. His blood pressure was remained around 80/40 mmHg after loss of consciousness, but he could not maintain his airway patent. So we lowered the infusion rate to 3.0 mg/kg/hr, immediately. The oxygen saturation was maintained above 95% with nasal oxygen supply, and blood pressure was maintained around 100-80/60-40 mmHg. After the sedation of 110 minutes with propofol (the infusion rate to 3.0-5.0 mg/kg/hr), he fully regained consciousness, and was discharged without complication after 1 hour observation. In case of post-Fontan patient, intravenous deep sedation with propofol was safe and effective method of behavioral management during dental treatment.