A unit dose dry powder inhaler has a dispersion chamber, optionally including one or more beads. A blister is supported adjacent to the dispersion chamber. A mouthpiece cover is removable from a mouthpiece, with movement of the mouthpiece cover causing the blister to open. An air flow path extends past or under the blister and into the dispersion chamber. As a result, the blister remains sealed until the inhaler is ready for use. The blister is then automatically opened when the mouthpiece cover is removed from the mouthpiece. Pharmaceutical dry powder is released from the blister and entrained in air flow through the inhaler, when the user inhales on the mouthpiece. The powder is dispersed in air within the dispersion chamber.