A 60-year-old man presented to the emergency department with lower gastrointestinal bleeding and minimal abdominal pain. Computed tomography (CT) showed superior mesenteric vein thrombosis (SMVT). He was treated with anticoagulant therapy and observation resulting in clinical improving and almost complete resolution of the thrombus. The symptoms and signs of SMVT are varied and non-specific. CT is very helpful in the diagnosis of SMVT. We recommend nonoperative therapy with anticoagulation and observation in patient who do not have the signs and symptoms of peritonitis.