Protein-losing enteropathy (PLE) is a rare and life-threatening complication that occurs after the Fontan procedure. We herein report the case of an 11-year-old Japanese boy who developed PLE six times after undergoing the Fontan procedure. High-dose spironolactone therapy has been effective for 2 years. His high level of serum aldosterone decreased to a nearly normal range and spironolactone may have a diuretic and anti-inflammatory potential.