Quadricuspid aortic valve is a rare congenital heart defect usually detected by echocardiography or at the time of aortic valve surgery. Preoperative recognition of this abnormality has clinical significance because it is frequently associated with other congenital cardiac abnormalities and anomalies of coronary origin. We report a case of quadricuspid aortic valve, which was detected preoperatively by transthoracic echocardiography and was associated with severe aortic regurgitation.