The diaphragm is especially important in sustaining minute ventilation in the neonate. Consequently, diaphragmatic paralysis is not tolerated well by the neonate and often results in prolonged respiratory failure. We experienced a case of unilateral diaphragmatic paralysis with the brachial plexus palsy in a male newborn infant who presented with apnea and cyanosis due to birth asphyxia. After endotracheal intubation, mechanical ventilaton was started. At two weeks after therapy, chest X-ray showed atelectasis and elevation of the right hemidiaphragm. The diagnosis of unilateral diaphragmatic paralysis was confirmed by real-time ultrasonography. At 4 weeks old, after several unsuccessful attempts at weaning from ventilatory support, right hemidiaphragm was plicated. On the second postoperative day, he could be weaned from ventiatory support without difficulty. He was doing well at follow-up 3 months later.