Coronary vasospasm is one of the most dangerous and fatal complications of coronary artery bypass grafting (CABG) operation. Our experiences in recent 2 cases happened during off-pump CABG (OPCAB) are presented. Case 1: A 63-year-old male who had 3 vessels disease underwent OPCAB using left internal thoracic artery (LITA) and the radial artery. When the sternotomy was going to be closed, ST elevation of electrocardiogram (ECG) occurred and was followed by ventricular fibrillation. Intra-aortic balloon pumping (IABP) and percutaneous cardiopulmonary support (PCPS) were applied immediately and an additional grafting to first diagonal artery (D 1) was carried out using a saphenous vein. Case 2: A 67-year-old male underwent OPCAB using LITA and the radial artery. ST elevation of ECG suddenly occurred and was followed by complete atrio-ventricular (AV) block when the sternum was closed. IABP and the ventricular pacing were applied immediately. While OPCAB may be less invasive operating method than conventional CABG, we should pay more attention to the coronary vasospasm.