Plants: small to medium-sized, in loose to dense, rarely fragile tufts, green, yellowish, brownish, or golden green, with orange tinge due to leaves yellow-green and stems reddish. Stems: creeping, ascending, or sometimes erect, densely or loosely terete- or subcomplanate-foliate, sometimes julaceous, regularly or irregularly pinnate, branches similar or more strongly complanate-foliate; central strand present; pseudoparaphyllia acute; axillary hairs of 2–3(–4) cells. Stem: leaves erectopatent to erect, imbricate or falcate-secund, lanceolate to ovate, slightly to strongly concave, not to moderately plicate; base short-decurrent; margins serrate, serrulate, or subentire; apex gradually tapered or acuminate; costa to (20–)40–80% leaf length, thin or thick distally, terminal spine present or sometimes absent; alar cells subquadrate or short-rectangular, small, walls moderately thick; laminal cells elongate to linear, smooth or occasionally prorate on dorsal surface, walls moderately thick; basal cells undifferentiated or slightly broader than adjacent cells, walls moderately incrassate, region clear or opaque across base. Branch: leaves smaller, somewhat narrower; costal abaxial surface more strongly serrate. Sexual: condition autoicous (synoicous in B. fendleri); perichaetial leaf acumen reflexed. Seta: red-brown to reddish orange, rough, smooth, or roughened proximally and smooth distally. Capsule: inclined, horizontal, or pendent (sometimes erect in B. fendleri), red-brown, remaining partly greenish until almost mature, ovate, elongate, or cylindric, usually curved; annulus separating in fragments; operculum bluntly short-conic; peristome xerocastique, perfect to moderately reduced. Calyptra: naked. Spores: 9–21 µm. Nearly worldwide.

Species 15–20 (6 in the flora). Brachytheciastrum was recognized as an infrageneric group within Brachythecium, as the velutinum group or sect. Velutina De Notaris, until M. S. Ignatov and S. Huttunen (2002) found that it is more closely related to Homalothecium than to Brachythecium (in the strict sense) and segregated it as a genus. However, there is little in common between Brachytheciastrum and Homalothecium in morphology, except the tendency of the leaf marginal teeth to stand at a wide angle, often perpendicular to reflexed, as well as the rather thick-walled laminal cells. Both genera are among the most xerophytic in the family and are more diverse in western North America.