Protein-losing enteropathy is a severe complication of Fontan surgery and is associated with anaemia. Few studies have reported on the efficacy of an intravenous iron infusion for treating protein-losing enteropathy and low albuminemia after Fontan surgery. Herein, we present two cases of female patients who suffered from protein-losing enteropathy and low albuminemia following Fontan surgery, both of whom improved after an intravenous iron infusion.