Non-occlusive mesenteric ischemia( NOMI) after cardiac surgery is a rare but catastrophic complication. Although NOMI is generally recognized to be associated with extracorporeal circulation, we present a fatal case of a patient who developed NOMI after off-pump coronary artery bypass grafting (OPCAB). An 85-year-old man with left main trunk and triple vessel disease underwent OPCAB. He developed severe abdominal pain with metabolic acidosis 9 hours postoperatively. Selective angiography of the superior mesenteric artery( SMA) showed narrow and spastic branches of the SMA. A continuous intra-arterial perfusion with papaverine was started, but he died of multiple organ failure on the 3rd postoperative day. We emphasize the importance of early diagnosis and adequate treatment of NOMI including prompt exploratory laparotomy.