Brachiaria serrata is a densely or loosely tufted rhizomatous perennial grass, 300-750 mm high, with the vegetative parts very variable and the basal sheath silky hairy. The culms (stems) are single or profusely branched. Leaves form a dense tuft at the base or are cauline leaving the base bare.

The leaf blade is 50-250 x 2-10 mm, the leaf margin is ± cartilaginous, white and usually crinkled; the ligule is a fringe of hairs. The raceme is 10-25 mm long, secund; rachis less than 1 mm wide, solid, triquetrous or crescentric, sometimes narrowly winged; the spikelets cover the whole length of the rachis, arranged in two rows; the pedicels are of equal length. The spikelet is 2.3-4.5 mm long, stipe absent, with dense, long, silky, white or purple hairs concentrated at the apex; the lower glume (the bracts at the base of the spikelet) is half as long as the spikelet and not separated from the upper lemma by an internode, and is 3-nerved; the lower lemma is acute or rounded, with a short stout mucro or awn up to 1.5 mm long and the lower palea is similar; the upper lemma, which encloses the grass flower, is ovate, striate, acute, rugulose; the anther is 1.0-2.5 mm long.

Flowering time: October to May.