A 75-year-old woman underwent emergency coronary artery bypass surgery after acute anterior wall myocardial infarction. Because of the presence of a local peritonitis, an emergency laparotomy was performed in which necrotizing Meckel's diverticulum was found and resected. Microscopically, sections through the diverticulum revealed a fresh thrombus occluded the arterial lumen of diverticulum. The patient had an uneventful postoperative course. We believe that the cause of Meckel's diverticulum ischemia was the development of atrial fibrillation with left atrium thrombus formation followed by embolic obliteration of Meckel's diverticulum feeding artery.