It has a single channelled, dark to reddish green leaf and up to fifteen blue flowers.

The lobe on top of the anther has yellowish red edges and the arms on the sides of the column have tufts of yellow or orange hairs.

The lobe on top of the anther is short with yellowish red edges and has finger-like calli.

[2][3] Thelymitra formosa was first formally described in 1884 by William Colenso from a plant collected between Norsewood and Dannevirke, and the description was published in Transactions and Proceedings of the New Zealand Institute.

[1][4] The specific epithet (formosa) is Latin word meaning "beautifully formed", "comely" or "handsome".