A 63-year old man was referred to our hospital with dyspnea on exertion and palpitation. An echocardiogram disclosed aortic stenosis and regurgitation, mitral regurgitation and tricuspid regurgitation. During cardiac catheterization, the right coronary ostium could not be cannulated, by coincidence, showed ventricular outpouching. Preoperative contrast-enhanced CT showed the partition wall isolating the right coronary ostium and the left ventricular outpouching in the subaortic valve area. The patient underwent aortic valve replacement after resection of the rudimentary right coronary cusp, and we resected the outpouching and closed the orifice with mattress sutures from the inside of the LV and the outside. Histopathology demonstrated that the resected outpouching was congenital fibrous left ventricular diverticulum.