A 12-year-old boy visited the emergency room for severe dyspnea. He was diagnosed with tuberous sclerosis at 5 years of age, and right ventricular dysplasia was detected at 11 years of age. Thromboemboli in right ventricle and bilateral pulmonary arteries were confirmed with two-dimensional echocardiography and computed tomography. We report the case of a patient with tuberous sclerosis who presented with huge thrombi in a dysplastic right ventricle and massive bilateral pulmonary thromboemboli without evidence of a cardiac tumor.