A three-month-old girl was referred to pediatric cardiology unit for evaluation of mild cyanosis and murmur. Chest roentgenogram revealed a boot-shaped heart. Echocardiography demonstrated subaortic ventricular septal defect, aortic override and infundibular stenosis. Then, the patient diagnosed as tetralogy of Fallot (TOF). Cardiac catheterization and angiocardiography revealed infundibular narrowing, hypoplasia of the right pulmonary artery and the enlarged right internal mammary artery originating from the right subclavian artery supplied blood flow into the right lung. The patient was performed complete repair. Post-operative period was uneventful. This is the first report presented about a case which pulmonary blood flow is provided by the enlarged right internal mammary artery in TOF associated with hypoplasia of the right pulmonary artery.