Mucopolysaccharidosis (MPS) syndrome is an inherited metabolic disorder. In more than half of the patients with MPS syndrome, heart valve involvement is reported; however, combined aortic and mitral valve stenosis in MPS syndrome type I-S is very rare. We describe a 39-year-old man with severe mitral and aortic valve stenosis due to MPS syndrome type I-S. Transthoracic and transesophageal echocardiography revealed severe thickening and calcification in the aortic and mitral valves with severe left ventricular hypertrophy. The coronary arteries were normal in angiography.