Tufted bulrush is a graminoid, 1-4dm tall, with very densely tufted stems that are smooth, roundish, and on a short, freely rooting rhizome. It has one brown, terminal spikelet, 4-6mm, several-flowered, with 2-3 empty scales at the base, often deciduous as the spikelet approaches full maturity. The lowest scale has a prominent, broad, blunt awn (1-3mm) that may shortly surpass the spikelet, anthers are 1.1-2.5mm. Its achenes are three-angled, brown, 1.5-1.7mm, with a small, slender point at the tip. It has several conspicuous, light brown scale-leaves at the base, a single, more normal leaf with a typical sheath but a slender blade, only 4-6mm, a little higher.
It is distinguished from similar species by its solitary spikelet, lack of a conspicuous, leaf-like bract subtending the spikelet, round stem, and cespitose habit.