Awned sedge is a loosely tufted grass-like perennial that grows in patches. There are two kinds of stems on the plants. One type has flowers and fruits (reproductive stems) and the other lacks these structures (vegetative stems). Reproductive stems are less common than the vegetative stems and are often lacking. Reproductive stems are 35-125 cm tall. Leaves are 3-10 mm wide, usually hairy, and are clustered towards the top of the vegetative stems. The upper half of the reproductive stems have 3-11 narrowly cylindrical flower/fruit clusters (spikes). The upper 1-6 are composed of male flowers. The lower 2-5 spikes are mostly composed of female flowers which mature into fruits (perigynia). The fruits are 6.5-12.0 mm long and have a two pronged beak at their apex (Mackenzie 1931-1935, Reznicek and Catling 2002).

Many times reproductive culms are absent and identification needs to be done using vegetative material. Therefore, botanists should learn to identify this species vegetatively. Still, it is easier to identify this species when plants have immature to mature perigynia.

Carex atherodes differs from many other Carex species by possessing hollow true vegetative culms which have nodes and internodes. Carex trichocarpa, also a member of section Carex, is somewhat similar. Care trichocarpa can be distinguished by its pubescent perigynia, glabrous leaf blades and sheaths, strongly reddish purple summits of distal leaf sheaths, and solid vegetative culms. In comparison, C. atherodes has glabrous perigynia, usually pubescent leaf sheaths and abaxial surfaces of leaf blades, pale brown to dull reddish purple summits of distal leaf sheaths, and hollow vegetative culms. Carex lacustris which can be found with C. atherodes and also can grow in dense monospecific patches differs in having leaf blades glaucous and lacking true vegetative culms.