Abstract: The present invention is directed to a mouthpiece to be used in association with nCPAP systems to prevent leakage from the mouth during nCPAP treatment. The mouthpiece is comprised of a thin flexible disk that fits between the user's lips and teeth and seals the mouth around the interior of the lips to prevent air from escaping. The mouthpiece does not need to be custom-fitted by to the user. In a preferred embodiment, the mouthpiece of the present invention further comprises a bite block, affixed to the interior surface of the disk, configured to position the user's lower jaw to open the user's airway. In a most preferred embodiment, the disk of the mouthpiece of the present invention contains a one-way valve which allows the user to breathe air in through the disk, but prevents air from flowing out through the disk when the user exhales.