A 78-year-old man presented at the emergency department with anterior chest pain. Coronary angiography (CAG) revealed three-vessel disease and percutaneous transluminal coronary angioplasty (PTCA) was performed on the right coronary artery. A preoperative plain chest computed tomography (CT) scan revealed hyperostosis of the sternum and clavicle. The patient underwent elective coronary artery bypass surgery 49 days later. During surgery, the thickness of the sternum caused difficulties with implementing median sternotomy. The pleura was also thicker than usual and even pulsation of the left internal thoracic artery (LITA) could not be determined due to severe adhesion. We harvested the right internal thoracic artery (RITA) instead of the LITA. The RITA was in a similar condition, but a 5 cm proximal portion could be prepared. The saphenous vein graft was anastomosed to the left anterior descending coronary artery after proximal anastomosis to the ascending aorta with the heartstring device because of the calcified aorta. The RITA-saphenous vein composite graft was anastomosed sequentially to the distal right coronary and circumflex artery. The patient's postoperative course was uneventful but he complained of numbness and lassitude of both upper extremities for one month. A postoperative contrast-enhanced CT scan revealed a patent LITA surrounded by thick tissue, indicating inflammatory disorders. The CT findings indicated a diagnosis of sternocostoclavicular hyperostosis. The postoperative CAG findings indicated that all bypass grafts were patent and the patient was discharged 32 days after surgery. Sternocostoclavicular hyperostosis is an inflammatory disease that might require surgeons to carefully reconsider graft selection.