A 7-month-old girl with failure to thrive, who, on clinical and diagnostic evaluation [echocardiography & CT angiography] to rule out congenital heart disease, revealed a rare vascular anomaly called systemic artery to pulmonary venous fistula. In our case, there was dual abnormal supply to the entire left lung as(1) anomalous supply by normal systemic artery [internal mammary artery](2) and an aberrant feeder vessel from the abdominal aorta. Left Lung had normal bronchial connections and normal pulmonary vasculature. The fistula drained through the pulmonary veins to the left atrium leading to 'left-left shunt'. Percutaneous intervention in two stages was performed using Amplatzer vascular plugs and coil embolization to close them successfully. The patient gained significant weight in follow up with other normal developmental and mental milestones.