A nasal mask configured to be as unobtrusive as possible while providing an air-tight seal around the nose of a wearer comprises a flexible nasal cup having a nasal opening formed by an inner circumferential edge or rim thereof and opening into a nasal chamber. The cup also includes inner and outer sealing flanges extending around the rim for forming an air-tight seal during use. The nasal cup is sized such that, when the nasal cup is positioned over a wearer's nose, the rim generally extends across the wearer's upper lip, around the alae of the nose, and across the dorsum of the nose. Opposite ends of a malleable strip are secured to the outer sealing flange and the strip extends across the portion of the outer sealing flange adapted to be positioned over the nasal dorsum. The strip is manually adjustable so that a user may selectively adjust the shape of the mask about the nose to improve the seal across the nose. An airflow passageway extends through the mask at an outer end thereof and is in flow communication with the nasal chamber for delivering air to and removing exhaled air from the nasal chamber. The nasal mask is specifically shaped to provide adequate air-flow to the wearer's nose.