A 69-year-old man noticed pain from his neck to his upper limbs, and two days later developed orthopnea. He was simultaneously aware of being unable to sip noodles. He was referred to our department. In addition to constrictive ventilatory impairment that worsened in the supine position, paradoxical breathing, bilateral-diaphragm immobilization observed on chest X-ray and a positive sniff test were apparent only when he was in the supine position. Therefore, we diagnosed him with bilateral phrenic nerve paralysis. His orthopnea was released by noninvasive positive pressure ventilation. Afterward, based on the preceding pain in both shoulders and a winged scapula, the original disease turned out to be neuralgic amyotrophy. In diagnosing bilateral phrenic nerve paralysis, it should be noted that the characteristic symptoms, signs and test results were apparent only in the supine position, and the inability to sip noodles may be a unique symptom in that it is manifested even in the sitting position.