Deer's hair sedge is a densely tufted grass-like perennial. The stiff and narrow stems are 5-45 cm tall. The leaves are inconspicous and mostly appear as scales at the base of the stem. One leaf occurs further up the stem. At the tip of the stem is a tiny (up to 1/4 inch long) cluster of small inconspicuous flowers (spikelet). Each spikelet contains between 3-9 flowers enclosed at the base by small scales. The fruits are one seeded, hard walled, and less than 1/16th of an inch long (Fernald 1970, Crins 2002).

This species is easiest to identify when it is in flower or fruit. Specimens should include full culms including the basal sheaths.

Trichophorum cespitosum can be distinguished from the three other Trichophorum spp. that occur in New York by its smooth, round to nearly round stems compared to the scabrous, triangular stems of the three other taxa.

Although not recognized by Crins (2002) and other authors (Gleason and Cronquist 1991, Haines and Vining 1998), Fernald's var. delicatulus is distinguished by less stiff stems, blackish or lead colored basal sheaths, and calcareous habitats.

Some Eleocharis species can look superficially similar with upper leaves that are without distinct blades and achenes that are terminated by tubercles. Eriophorum vaginatum perhaps could look superficially similar as well. It has at least 10, long, cottony-white, hairlike perianth bristles, and 10 or more empty sterile scales at the base of the spikelets.