Aortic root aneurysm after orthotopic heart transplantation (HTx) is rare. It may originate from cystic medial necrosis of the donor heart aorta. Herein we have reported a 64-year-old man who received an orthotopic HTx due to dilated cardiomyopathy. Although asymptomatic, follow-up echocardiography revealed dilatation of the aortic root and severe aortic regurgitation at 3 years after the transplantation. He underwent a Bentall procedure with a prosthetic valved conduit. The post-operative course was uneventful. This case demonstrated that a heart-transplant recipient with a late aortic root aneurysm can be successfully treated with an excellent outcome.