Objective: In Japan, only a few reports of the Ross procedure in neonates and infants have been published. The objective of this study was to evaluate the outcome of patients undergoing a Ross procedure before the age of one year, and to review the validity of opting for this procedure at this age. Methods: The records of 13 infants (including three neonates) undergoing a Ross procedure between December 1996 and June 2017 were reviewed. Major outcomes studied included graft-associated morbidity, autograft function, and the need for reoperation. Results: The median age at the time of Ross procedure was 166 days, and median weight was 5.7 kg. Primary diagnoses were aortic stenosis in 10 cases and aortic insufficiency in three. Nine cases required emergent Ross procedure due to left ventricular dysfunction refractory to medication, requirement of mechanical ventilation or intravenous inotropic drugs. Concomitant procedures included three aortic coarctation repairs, two annular enlargement procedures with a Konno incision and one each of aortic and mitral annuloplasty. The mean cross-clamp time was 131 min and the mean extracorporeal circulation time was 178 min. Two cases required extracorporeal membrane oxygenation. Seven underwent delayed sternal closure and four required postoperative peritoneal dialysis. The median duration of mechanical ventilation was five days and the median length of intensive care unit stay was seven days. Survival was 100% at a median follow-up of 9.9 years. The diameter of the aortic annulus mostly stayed within normal limits, although sinus of Valsalva's enlargement beyond normal value was noted in some cases. Trans-aortic valve pressure gradient was less than 20 mmHg and aortic insufficiency was less than mild in all cases, thus requiring no reintervention for the valve. Two cases required coronary arterial bypass and release of the subaortic stenosis. Freedom from reoperation for the left heart was 100% at one year, and 81.5% at five years and 10 years. Ten cases required reoperation for the right heart, and freedom from reoperation was 84.6% at one year, 29.7% at five years and 9.9% at 10 years. Conclusion: Durability of the pulmonary autograft was excellent. The Ross procedure can be an effective treatment strategy for severe aortic valve diseases in neonates and infants.