The mitral valve aneurysm is a rare complication of infective endocarditis involving mitral or aortic valve. The perforation of the mitral valve aneurysm can lead to significant mitral regurgitation (MR) or thromboembolism, which can cause sudden hemodynamic deterioration. We describe here a case of healed infective endocarditis of the aortic valve with ruptured mitral valve aneurysm that led to severe MR. The aneurysm of the anterior mitral leaflet was diagnosed by two-dimensional transthoracic echocardiography. In this case, three-dimensional transthoracic echocardiography demonstrated the detailed morphology of mitral valve aneurysm which resulted in successful surgical repair of the aneurysm.