A 3-month-old boy with coarctation of the aorta (CoA), ventricular septal defect (VSD), atrial septal defect, and severe pulmonary hypertension (PH) underwent one-stage repair consisting of patch closure of VSD and coarctation repair. Inhalation of nitric oxide (iNO) was commenced to treat residual severe PH on the day of the operation. Oral sildenafil citrate was commenced on the day 1 and iNO was gradually weaned off on the day 3. There was no "rebound", severe increase in pulmonary artery pressure, which commonly occurs after discontinuation of iNO. Then the patient was extubated without any difficulties or recurrent PH. The oral sildenafil citrate therapy was ceased on the day 8. Prophylactic use of oral sildenafil citrate for PH might be an useful alternative to shorten the duration of iNO therapy and intensive care unit (ICU) stay in the selected patients after congenital open heart surgery.