Protein Loosing Enteropathy (PLE) is a disorder characterized by either increased loss of proteins from the digestive system or defect in the absorption of proteins. It is a rare complication seen in some cases of Fontan surgery, the reason for which remains an enigma. There are many causes elucidated like increased central venous pressure, decreased cardiac output, increased mesenteric resistance, lymphatic obstruction and so on. Though panoply of treatment options is available for the management of PLE post Fontan, there is still no consensus regarding the causes, consequences and treatment protocol. We present a case of 22 year old girl who underwent Fontan procedure for complex congenital heart disease at the age of 3. She developed diarrhea, hypoproteinemia, hypoalbuminemia, hypocalcemia 18 years after surgery and was diagnosed as protein loosing enteropathy post Fontan based on strong clinical findings after excluding other causes of hypoalbuminemia and was managed conservatively. PLE post Fontan has a grave prognosis and is essential to elucidate the exact pathophysiological abnormality thus paving way for better therapeutic management.