An adjustable nasal cavity dilator is provided that enables a user to selectively dilate a single nasal passageway in order to achieve a desired flow of air therethrough. In an exemplary embodiment, the nasal cavity dilator comprises an elongate foundation strip and a dilation adjustment band. An adhesive material secures the nasal cavity dilator to the external tissue of a user's face, on the side of the nasal cavity, and on the adjacent cheek. A fastener secures the dilation adjustment band to maintain the force that keeps the nasal cavity in the dilated state. In another embodiment, an attachment is coupled to the foundation strip in order to slidingly engage the dilation adjustment band so that it reverses direction before the force is applied. A free end of the band is then fastened to either the foundation strip or the dilation adjustment band.