A 47-year-old woman was referred from a regional hospital for surgical myocardial revascularization after non-ST-elevation myocardial infarction. Medical history reported dyslipidaemia, hypothyroidism, endometriosis surgery, and a family history of thromboembolism. Coronary angiogram and transthoracic echocardiography (TTE) performed 13 days earlier showed two-vessel coronary disease with severe stenosis of the left anterior descending (LAD), diagonal and marginal arteries, and preserved left-ventricular ejection fraction (LVEF = 55%) without significant valve disease. Intraoperative transoesophageal echocardiography (iTEE) showed a large mass attached to the aortic non-coronary leaflet and sinus of Valsalva (Panel A, white star), with reduced leaflet motion but no valvular hemodynamic dysfunction (Panel A). The mass was closely attached to and moving with the leaflet, but clear cleavage planes with the leaflet and the aortic root were observable (Panel A, white triangles). An organized thrombus secondary to an initial lesion by the catheter during coronary angiogram was suspected, and confirmed by the macroscopic and histological examination (Panel B). The thrombus was completely removed, and myocardial revascularization by sequential left internal thoracic graft to the diagonal and LAD as well as radial Y-graft to the marginal artery was performed. Post-bypass iTEE examination showed complete thrombus removal and normal motion of the leaflet (Panel C). On the basis of familial history of thrombus, our consultant haematologist recommended oral anticoagulation therapy with warfarin until results of blood coagulation disorder tests are obtained. The patient was discharged 6 days after surgery without significant post-operative complication.