Bromus japonicus is an annual or biennial tufted grass growing 0.2–1 m (7.9 in – 3 ft 3.4 in) high.

The densely hairy leaf blades are 10–20 cm (3.9–7.9 in) long and 2–4 mm (0.079–0.157 in) wide.

The divergent branches are typically longer than the purplish spikelets and are ascending or spreading.

The margins of the lemmas roll slightly inwards at maturity, and the twisted and strongly divergent awns are 8–12 mm (0.31–0.47 in) long.

[3] The grass is native to Eurasia but has been naturalized throughout the United States and southern Canada and is rare in the Yukon.