Systemic-to-pulmonary artery shunts using polytetrafluoroethylene (PTFE) (modified Blalock-Taussig shunt) are being used successfully in palliation of cyanotic congenital heart diseases. Graft thrombosis is by far the most common complication of the procedure. Persistant serum leakage through PTFE graft causing perigraft seroma is a rare but devastating complication resulting in increased duration of tube drainage or reinsertion of chest tubes, prolonged hospital stay, and multiple operations. Two consecutive modified Blalock-Taussig shunts complicated by perigraft seroma formation are presented here with review of the literature.