Acute pancreatitis can result in many vascular complications in both artery and vein. Venous complication usually occurs as a form of splenic or portal vein thrombosis, and also can simultaneously occur in superior mesenteric vein as well. Rarely, isolated superior mesenteric vein thrombosis occurs as a venous complication. Although it is uncommon, mesenteric vein thrombosis is an important clinical entity because of the possibility of mesenteric ischemia and infarction of small bowel. The treatments of mesenteric venous thrombosis include anticoagulation therapy, transcatheter therapy and surgical intervention. We report a case of 45-year- old man who had acute pancreatitis with isolated superior mesenteric vein thrombosis, which was spontaneously dissolved with the resolution of underlying inflammation without anticoagulation or surgical intervention.