It is an erect, slender shrub with narrowly egg-shaped leaves with a heart-shaped base, and pink to purple flowers.

[4][5] The specific epithet (brachystachys) means "a short flower spike".

[6] This thomasia grows in heath and shrubland or in forests near watercourses and swamps in near-coastal areas from Yallingup to Pemberton, and further east to the Stirling Range and Porongurup National Parks.

[2][3] Thomasia brachystachys is classified as "not threatened" by the Western Australian Government Department of Biodiversity, Conservation and Attractions.

[3] This thomasia is described as a dramatic species that has proved reliable in a range of conditions when grown in well-drained soil, but appreciates water during dry periods.