Plants cespitose. Culms terete or nearly so, 20-70 cm, smooth. Leaves: bladeless sheaths 1-3, evenly distributed on culm, distal to middle, not inflated distally, filiform, channeled, 0.4-1.2 mm wide. Inflorescences: involucral bracts absent. Spikelets solitary, erect, globose, 10-20 mm in flower, 20-35 mm in fruit; proximal empty scales usually 7 or more, ascending, blackish, ovate-lanceolate, 5-10 mm, thin, margins broad, ribless, midrib not reaching tip. Flowers: perianth bristles usually more than 8, creamy white to pale brown, 10-20 mm; anthers 0.5-2 mm. Achenes oblanceoloid, (1.8-)2-2.3(-2.7) × 0.5-1.2 mm; apex minutely apiculate, 0.1 mm. 2n = 58.
Eriophorum brachyantherum var. pellucidum Lepage is ca. 30 cm with narrowly oblong achenes (2.5-2.7 mm). It is known from only a single station (Rupert House, Quebec) and may be a hybrid between E. brachyantherum and E. vaginatum subsp. spissum. Further study is needed to determine the status of this plant.