Quadricuspid aortic valve is a rare congenital abnormality; it is usually an isolated lesion, but several concomitant congenital abnormalities have been described. We report a case of congenital quadricuspid aortic valve associated with obstructive hypertrophic cardiomyopathy. Two-dimensional (2D) transthoracic and transesophageal echocardiography and real-time three-dimensional (3D) echocardiography clarified the morphological and functional status of the aortic valve. To our knowledge, the association between quadricuspid aortic valve and obstructive hypertrophic cardiomyopathy has never been described before.