Case reports of severe idiopathic portal hypertension (IPH) requiring liver transplantation are very rare. We report the case of a 65-year-old woman who was diagnosed as having IPH. At the age of 60 years, her initial symptom was hematemesis, due to ruptured esophageal varices. Computed tomography of the abdomen showed splenomegaly and a small amount of ascites, without liver cirrhosis. She was diagnosed as having IPH and followed-up as an outpatient. Five years later, she developed symptoms of a common cold and rapidly progressive abdominal distension. She was found to have severe liver atrophy, liver dysfunction, and massive ascites. Living donor liver transplantation was then performed, and her postoperative course was uneventful. Histopathological findings of the explanted liver showed collapse and stenosis of the peripheral portal vein. The areas of liver parenchyma were narrow, while the portal tracts and central veins were approximate one another, leading to a diagnosis of IPH. There was no liver cirrhosis. The natural history of refractory IPH could be observed in this case. Patients with end-stage liver failure due to severe IPH can be treated by liver transplantation.