Pterostylis karri is a terrestrial, perennial, deciduous, herb with an underground tuber and a small rosette of leaves 10–20 mm (0.4–0.8 in) wide and 5–10 mm (0.2–0.4 in) although the rosette is absent in some specimens.

The dorsal sepal and petals are fused, forming a hood or "galea" over the column.

[2][3] Pterostylis karri was first formally described in 2014 by David Jones and Christopher French from a specimen collected south of Mandurah and the description was published in Australian Orchid Review.

[4] The karri snail orchid grows in moist places in shady forest and around granite outcrops between Walpole and Margaret River in the Jarrah Forest, Swan Coastal Plain and Warren biogeographic regions.

[2][5] Pterostylis karri is classified as "not threatened" by the Western Australian Government Department of Parks and Wildlife.