A case of transcatheter occlusion of a modified Blalock-Taussig (BT) shunt with a detachable balloon is described. A three month old boy with pulmonary atresia with intact ventricular septum had a repair consisting in valvotomy and a modified BT. This palliative aorticopulmonary shunt created congestive heart failure. As an alternative to surgery, a detachable balloon was used to occlude the BT shunt.