A 55-year-old man complained of acute onset of shoulder pain and dyspnea in the supine position. A diagnosis of bilateral diaphragmatic paralysis was made based on clinical inspection of his breathing pattern, radiographic appearance, and pulmonary function tests. He had had no traumatic or thoracic surgery or inflammatory episode. He did not suffer from diabetes, other central neural diseases, or any neoplastic disease. From the clinical feature and electromyographic findings, phrenic nerve involvement of brachial neuritis without any other muscle involvement was considered as a causative disease. When he received non-invasive intermittent positive-pressure ventilation by nasal mask in a supine position, his dyspnea was substantially attenuated and Carbon dioxide retention was lessened. After 1 year, his shoulder pain is still persisting and radiographic findings are not remarkably improved.