A 68-year-old man presented with severe abdominal pain. Seven months earlier, he had received systemic chemotherapy for small-cell lung cancer with solitary metastasis to the spleen, followed by splenectomy. Abdominal computed tomography and abdominal arterial angiography showed diffuse ischemia of the mesenteric artery without apparent occlusion. The patient also suffered from septicemia caused by Enterococcus faecium. Therefore, a diagnosis of non-occlusive mesenteric ischemia (NOMI) induced by septicemia was supposed. Although treatment with antibiotics and papaverine hydrochloride was administered and the necrotic tissue in the intestinal tract was resected, the patient died. Physicians should be aware that patients undergoing splenectomy are likely to be affected by septicemia, which may subsequently induce NOMI.