Bilateral phrenic nerve palsy after open cardiac surgery is an extremely rare complication, but serious enough to induce respiratory failure or cardiac arrest. We report a 76-year-old male patient presented weaning difficulty after elective aortic valve replacement and thymic resection under hypothermic cardiopulmonary bypass. Bilateral phrenic nerve palsy was diagnosed through chest radiograph and electrophysiological studies of the diaphragm. After receiving tracheostomy, invasive intermittent positive-pressure ventilation (IPPV) was applied to him at intensive care unit. He was referred to our hospital because of weaning difficulty which lasted for 6 months after the surgery. He received extensive pulmonary rehabilitation which includes non-invasive positive-pressure ventilation (NIPPV), and then he finally succeeded in weaning from ventilator after 8 months. Applying NIPPV to patients with bilateral phrenic nerve palsy could minimize the duration of IPPV, reduce its disadvantages, and facilitate weaning of artificial ventilation.