A 48-year-old man was treated for heart failure at a nearby hospital, and echocardiography revealed thrombi in both ventricles. He was referred to our hospital for a detailed examination and treatment. Coronary angiography was performed, and the results were #2-3 50%, #5 50%, #6 100%, and #11 75%. Echocardiography revealed diffuse hypokinesis with an ejection fraction (EF) of 31%, which was indicative of old myocardial infarction. The left intraventricular thrombus was floating and adherent to the apex of the heart, and we judged that immediate surgical intervention was necessary to remove the thrombus and perform coronary artery bypass grafting. The right ventricular thrombus was removed through the tricuspid valve with an incision in the right atrium using a rigid endoscope to ensure that no thrombus remained behind. There were no perioperative embolic complications, and oral administration of direct oral anticoagulants (DOAC) was continued for one year after the operation. However, no recurrence of thrombosis was observed, and the prognosis was good.