Acianthus sinclairii is a terrestrial, perennial, deciduous, sympodial herb with a single heart-shaped, glabrous, dark green leaf which often has a maroon tinge or markings.

The labellum is also shorter than the sepals, dished, broadly egg-shaped with the edges turned under, dull red with two rounded calli at its base.

[2][3][4] Acianthus sinclairii was first formally described in 1853 by Joseph Dalton Hooker and the description was published in The Botany of the Antarctic Voyage of H.M.

Discovery Ships Erebus and Terror in the years 1839–1843, under the Command of Captain Sir James Clark Ross.

[6] This orchid usually grows in shaded shrubland and forest, only rarely in sunny habitat but often near streams or moist areas.