A nasal delivery device for delivering substance to a nasal airway of a subject, comprising: a mouthpiece (919) through which the subject in use exhales to cause closure of the oropharyngeal velum of the subject； a nosepiece (917) for fitting to a nostril of a subject, the nosepiece including a nozzle (949) through which substance is in use delivered to the nasal airway； a manually-actuatable substance supply unit (920) for delivering substance through the nozzle of the nosepiece, wherein the substance supply unit comprises a body part (955) which is movable from a first, rest position to a second, actuated position on manual actuation of the substance supply unit； and a body member (921) which receives the substance supply unit, wherein the body member includes an inlet (925) which is in fluid communication with the mouthpiece and an outlet (927) which is in fluid communication with the nosepiece； wherein the inlet of the body member is opened when the body part of the substance supply unit is moved to the actuated position, thereby providing for an air flow through the nosepiece simultaneously with manual actuation of the substance supply unit.
