Purpose: Persistent vegetative state is a form of wakefulness without awareness. This report describes a dental appliance for the treatment of sleep breathing disorders in this condition. The device can be easily inserted and removed by the patient's family or nurse. Materials and Methods: A 19-year-old woman had been in a persistent vegetative state since having hypoxic-ischemic encephalopathy because of cardiopulmonary arrest. Although she exhibited a sleep-wake cycle and normal respiration, she had sleep apnea and snoring, and produced snoring-like sounds even in an awake state. A three-piece device with Herbst attachments was fabricated to treat the symptoms. Overnight sleep studies were carried out to evaluate the effectiveness of the appliance. Results: The device could be handled by the patient's family. Snoring was satisfactorily reduced after insertion of the device. Sleep apnea, desaturation, and minimal oxygen saturation were markedly improved. Conclusion: If the family of a persistent vegetative state patient wishes to treat sleep-disordered breathing, the appliance may be helpful as an alternative to relieve the symptoms. The device could be applied for sleep apnea patients who experience difficulties using other types of oral appliances.