Iatrogenic superior mesenteric arteriovenous fistulas (AVF) after gastrointestinal surgery are rare, especially in Japan, with only 28 cases being documented. We report a case of iatrogenic superior mesenteric AVF, which developed rapidly and detected at 26th day after a resection of small intestine for strangulated ileus. A 39-year-old man was emergently transfered to the hospital for strangulated ileus and underwent on excision of the necrosed small intestine. After the operation, abdominal pain and diarrhea persisted and a pul-sative tumor and continuous murmur in the middle abdominal part were confirmed on 26th postoperative day. Abdominal CT and angiography revealed a superior mesenteric AVF and a pseudoaneurysm. Successful resection of those were performed. The cause of AVF was considered to be related to the mass ligation of the mesenteric vessels in the primary operation. Postoperative course was uneventful.