The incidence of aneurysms of the pulmonary artery is known to be very low. Although diagnosis and evaluation of pulmonary artery aneurysms may be difficult without angiography, computed tomography and MRI's have emerged as useful noninvasive techniques. However, a transthoracic echocardiogram may reveal a pulmonary artery aneurysm. To our knowledge, transesophageal echocardiographic findings of pulmonary artery aneurysm with thrombus have not been reported in detail. Here, a case of thrombosed aneurysm of the main pulmonary artery diagnosed by transesophageal echocardiography and confirmed by computed tomography and MRI is reported.