We encountered a case of portal-systemic shunt encephalopathy cured by balloon-occluded retrograde transvenous obliteration (B-RTO). A 73-year-old man had been observed for membranous nephropathy at our hospital since 1987. There was no past history of liver dysfunction. He was admitted with encephalopathy. Abdominal enhanced computed tomography showed a portosystemic shunt through the inferior mesenteric vein and right internal iliac vein. We diagnosed hepatic encephalopathy due to this porto-systemic shunt, and B-RTO was performed. After B-RTO, he has not had repeated encephalopathy. B-RTO can be effective for portosystemic encephalopathy. Inferior mesenteric-right internal iliac shunt encephalopathy is rare and our patient is the first case of B-RTO performed in cases with this shunt.