This small herb has yellow-green, sparsely-branched stems that are 10-40 cm tall and the angles of the stems and the pedicels are smooth with no hairs. The calyx-tube is cup-shaped and its teeth are narrowly triangular and fringed with short glandular hairs. The pink corolla is tubular and flared at the top into spreading petal lobes. The tube (which is hairy on the outside and on the top of the inside) together with a lobe are 0.5-1.5 cm long with 2 yellow lines and some purple spots in the white throat. The lobes are notched at the top and the outsides are glabrous, but the margins are ciliate. The anthers are covered with dense white hairs. The yellowish-brown capsules have yellowish-brown seeds 0.04-0.06 mm long (USFWS 1995).

The plant must be in flower or fruit.

Agalinis setacea is the most closely related species in New York. It stems are dark green to purple-tinged and more branched. The leaves are more numerous and more narrow than Agalinis acuta. The corolla is larger, 1.1 cm to 2.1 cm long, pinkish-purple, and the exterior surfaces of the lower lobes are hairy instead of glabrous as in Agalinis acuta. There are no notches at the tops of the lobes. The seed color is dark brown to black, not yellowish-brown (USFWS 1995). Agalinis purpurea has similar-looking flowers but they are stalkless. Agalinis tenuifolia has smaller darker flowers with the petals facing forward and hairless on the inside, although the stamens have hairs and the top petals arch over them.