Although the type specimen was collected in the Sydney area in 1803, the species in now only known from three locations near Jervis Bay.

Prasophyllum affine is a terrestrial, perennial, deciduous, herb with an underground tuber and a single tube-shaped leaf up to 500 mm (20 in) long.

The labellum turns upwards at about 90° and there is a green to purple callus covered most of its upright part.

The fruit that follows flowering is a shiny green capsule which turns brown before releasing its seed.

[2][3] Prasophyllum affine was first formally described in 1810 by John Lindley from a specimen collected at Port Jackson and the description was published in The Genera and Species of Orchidaceous Plants.