Coleus australis is an erect or ascending perennial herb, growing from a fleshy tuberous base and sometimes becoming woody at the base, reaching heights of 1–5(–10) decimeters. The stems and branches of this plant are somewhat fleshy and densely villous. The leaves are simple, opposite, and vary in shape from ovate to suborbicular or broadly deltate, measuring 1.5–3(–9) cm long and 0.5–2(–3.9) cm in width. The leaves have a rounded to sometimes acute apex and a broadly cuneate to truncate or sometimes subcordate base, with villous-tomentose surfaces. The upper surfaces contain small oil globules, while the lower surfaces are glandular punctate with reddish glands. The flowers are in dense verticillasters (an inflorescence that resembles a whorl but consists of two crowded cymes on either side of the stem) of 6–12, arranged in terminal, racemose inflorescences 5–30 cm long, and can be simple or sometimes branched at the base. The calyx is actinomorphic, occasionally bilabiate, and becomes enlarged in fruit. The corolla is zygomorphic (bilaterally symmetric), pale blue, and much exserted, with a boat-shaped lower lip longer than the upper lip. The fruit are brown nutlets, ovoid to lenticular, and approximately 0.8 mm long. The seeds lack endosperm or contain only a scanty amount, which is oily. It is found in dry, exposed, and often rocky sites at elevations ranging from 0-1,310 meters.