We report a case of a 10-week-old girl, with tetralogy of Fallot and a Blalock-Taussig shunt, who presented with hypercyanotic episodes. She was found to have serous fluid leakage around her shunt, causing compression of her trachea. Hypercyanotic episodes resulting from shunt leakage have not previously been reported. An awareness of this possible complication of a Blalock-Taussig shunt will allow the emergency physician to consider it in the differential diagnosis of hypercyanotic episodes.