Plants light green or yellowish green. Stems 0.2-15(-25) cm. Leaves obovate to ovate-lanceolate, distal leaves 2-5 mm; margins toothed, sometimes nearly smooth distally; percurrent to rarely short-excurrent. Specialized asexual reproduction absent. Seta (1-)6-15(-30) mm. Capsule exserted, 1-3 mm, globose-pyriform when young, highly variable in shape when old, urceolate to pyriform; neck short, distinct; exothecial cells irregular hexagonal; suboral cells consisting of 5-17 rows of rectangular cells. Spores (24-)46-60(-90) µm, papillose.
Physcomitrium pyriforme is morphologically variable and widespread across the continent. Plant size, leaf characters, and shape of the capsule vary from place to place and often within populations.