Pedicularis langsdorfii is a short, compact plant of alpine tundra and meadows, with taproot and purple flowers. The leaves have a broad central vein, and are green with purplish edges, sometimes wholly purple. There are several stem leaves below the inflorescence, and long bracts intermixed with the flowers, distinguishing it from P. interior, which has few stem leaves. The plant may be hairy, but the hairs are long, and not densely wooly-hairy like P. lanata. Also, the upper petal of the flower has two small teeth. The lower petal is a paler pink than the hood, with three rounded lobes. The calyx is fused, with 5 triangular teeth. Fruits are a many-seeded dry capsule, 12-15 mm long.
Pedicularis langsdorfii is perennial, but produces new leaves and flowering stalks every year. It flowers early to mid-summer; the inflorescence elongates when plants fruit.
Pedicularis langsdorfii is monoecious with bisexual flowers. Flowers of P. langsdorfii is nectar-producing and bumblebee-pollinated. They are also protogynous—the pistil is mature before anthers of the same flower are releasing pollen. This timing prevents self-fertilization. A study in Atqasook, arctic Alaska, found that P. langsdorfii did not set seed if queen bees were excluded (Williams and Batzli 1982). In the control plants, approximately 50% of the flowers set seed. P. langsdorfii also spreads asexually by its roots (Macior 1975). Like other Pedicularis species, Langsdorf's lousewort is hemi-parasitic: it photosynthesizes but also steals water and nutrients from the roots of nearby plants.
Pedicularis langsdorffii is an arctic-alpine amphi-Beringian species, occurring from Kamchatka through the Alaskan and Canadian arctic to Greenland, also occurring in the low arctic and mountain ranges of the southern half of Alaska to the Yukon Territory and mountainous British Columbia beyond. In Alaska, this species occurs in tundra areas across the state, except for the southeastern panhandle. In Denali, P. langsdorffii occurs on both sides of the Alaska Range, although the species is less common on the south side, concentrated near Broad Pass and Shellabarger Pass.
This species is slightly more common on steep slopes. It is less common on north- or south-facing slopes. In Denali, this species is found at high elevations where the peak frequency is above 1100 m. Its range of elevations is fairly wide where it is found from 546 to 1734 m.