Blood cysts within the heart are very rare entities in adults. The authors present possibly the first ever case in which blood cysts were found on both mitral valve leaflets. A 65-year-old woman was referred for transthoracic echocardiography because of vague chest discomfort. Transthoracic echocardiography displayed echo-free cysts on the tips of both mitral valve leaflets. Subsequent transesophageal echocardiography confirmed this finding. The blood cysts were successfully surgically removed.