A 75-year-old man with a heart murmur and fatigability was referred to our hospital. We diagnosed unruptured giant right sinus of Valsalva aneurysm that obstructed the right ventricular outflow tract by echocardiography (UCG), computed tomography (CT) and magnetic resonance imaging (MRI). The right ventricle was dilated and its ejection fraction was decreased to 9.3% by MRI. Successful surgical repair involved the right sinus of Valsalva plasty using a bovine pericardial patch and resection of the aneurysm through only a right ventricular outflow incision. His postoperative course was uneventful.