A 70-year-old man injured his spinal cord at the fourth cervical vertebra due to a fall and became quadriplegic. Following emergency treatment, the patient was admitted to our hospital for rehabilitation. On admission, respiratory function tests indicated a percent vital capacity value (%VC) of 58.6%, revealing restrictive ventilatory impairment. After admission, we observed difficulty breathing at night and extreme snoring and thus performed a simple full-night polysomnography. Results showed an apnea-hypopnea index (AHI) of 46.5/hr and serious obstructive sleep apnea syndrome (OSAS). Based on these results, we conjectured that a preexisting OSAS condition was exacerbated by the cervical spinal cord injury, and thus administered nasal continuous positive airway pressure (NCPAP) in addition to respiratory rehabilitation. A speedy disappearance of clinical symptoms was found with the application of NCPAP. Compared to a 3% oxygen desaturation index (ODI 3%) of 31.0 dips/hr prior to treatment, the ODI 3% dropped to 3.5 dips/hr after 14 days, and 0 dips/hr after 60 days, indicating an obvious improvement in nocturnal oxygen desaturation.