Large mountain bittercress is a perennial wildflower of wet places. It is erect in habit with stems from 20-50 cm high arising from slender rhizomes from 2-2.5 mm thick. The lower stems range from glabrous to fairly densely haired with short, spreading and simple hairs. The long-petioled, simple, basal leaves are orbicular to ovate shape. They measure 3-7 cm long and 3-7 cm wide with heart-shaped bases and shallow lobed margins. The petioles are typically 2-5 times longer than the blades. The more numerous stem leaves are similar to those at the base but have slightly shorter petioles. The surfaces of all the leaves are glabrous to sparsely haired.
The inflorescence is a few-flowered raceme of white flowers. The spreading to ascending pedicels are 10-20 mm long and the glabrous sepals measure 3-4 mm long. The petals are spatulate-obovate in shape and measure 7-12 mm long. The stamens are slightly longer than the sepals. The fruits are straight, ascending siliques from 2-3.5 cm long and 1.5-4 mm wide.
Large mountain bittercress is a plant of wet places at middle elevations including seeps and streams and moist alpine meadows.
Large mountain bittercress may be found across much of the western United States and Canada.