Thunbergia atriplicifolia is a perennial shrublet about 250 to 400 mm tall. The stems are nearly upright (sub-erect) or grow along the ground but turn up at the tips (decumbent) and arise from a woody rootstock that produces milky sap. The plant is densely to sparsely covered with soft, whitish hairs. The leaves are stalkless or with a very short petiole up to 4 mm long, green, softly hairy, about 20-60 x 12-35 mm and 3-5 veined at the base. Their shape is oval or elliptic to lanceolate, the tip may be acute, obtuse or notched, and almost rounded to heart-shaped (cordate), cut nearly straight (truncate) or wedge-shaped (cuneate) at the base. The margin is entire or toothed, usually with two teeth at the base. Flowers are borne in the axils of the leaves, on a long pedicel. The flowers are about 50 mm wide, creamy yellow, with a tube about 25 mm long and 2-10 mm wide, yellow on the inside. The style is longer than stamens. The bracts are 15-25 mm long and persistent. The flowering period is in summer, between October and April. The fruit is a capsule with a globose base, about 15-19 mm long, releasing greyish or reddish brown seeds with trichomes. T. triplicifolia is distinguished from related taxa by its slender stems and almost sessile leaves that are densely crowded in the upper part.