Banksia epimicta is a prostrate, spreading shrub with its stems more or less on the ground and that forms a lignotuber. It has crowded, pinnatifid leaves that are linear in outline, 110–330 mm (4.3–13.0 in) long and 7–14 mm (0.28–0.55 in) wide on a petiole up to 30 mm (1.2 in) long, with between ten and thirty-five sharply-pointed, curved teeth on each side. The flowers are borne on a down-turned head containing between forty-five and seventy pungent-smelling flowers in each head. There are broadly linear to egg-shaped, dull brown involucral bracts 40–50 mm (1.6–2.0 in) long at the base of the head. The flowers have a creamy white and pale yellow perianth 43–52 mm (1.7–2.0 in) long and a curved, cream-coloured pistil 45–58 mm (1.8–2.3 in) long. Flowering occurs from July to September and there are several more or less glabrous follicles 18–19 mm (0.71–0.75 in) long in each head.^[2][3][4]

This banksia was first formally described in 1996 by Alex George in the journal Nuytsia and given the name Dryandra epimicta from specimens collected in 1986 near Kulin.^[2][5] In 2007, Austin Mast and Kevin Thiele transferred all the dryandras to the genus Banksia and this species became Banksia epimicta.^[6][7] The specific epithet (epimicta) is derived from the ancient Greek word mykter, meaning "a nose" or "a nostril" with the prefix epi- meaning "upon", referring to the strong, unpleasant smell of the flowers.^[2]

Banksia epimicta grows in kwongan and shrubland in a small area near Kulin where only about one hundred plants were known in 1990.^[3]

This banksia is classified as "Priority Two" by the Western Australian Government Department of Parks and Wildlife^[4] meaning that it is poorly known and from only one or a few locations.^[8]