Heart-leaved twayblade is a perennial with stems to 20 cm tall. It consists of a single stem, with a pair of clasping leaves at mid stalk. The leaves are about 4 cm in length, broadly heart-shaped, with parallel leaf venation. They are opposite of each other on the stem. The stalks are smooth to glandular hairy above the leaves.
The flowers are pale green to purplish-brown in color, with the lip divided into 2 linear lobes with a pair of horn-like teeth at the base.. The 5 to 16 flowers form an elongated, terminal raceme.
Heart-leaved twayblade is a plant of damp, mossy places, often found along streams or in bogs. It may on occasion be found in dry forested areas or on open slopes.
Heart-leaved twayblade is found from Alaska to Greenland. On the east coast, it may be found as far south as North Carolina, in the Midwest, it is found as far south as Minnesota and Michigan, and in the west as far south as New Mexico and California. It is found in the mountainous areas of both Oregon and Washington.
In the Columbia River Gorge, it may be found east of Multnomah Falls to about adjacent to the Little White Salmon River. Within that range, it may be found between the elevations of 100'-4000'.