It has a single fleshy, channelled leaf and up to six strongly scented, dark blue to purple flowers and often grows in clumps.

The lobe on the top of the anther is yellow with a dark brown or blackish band and a shallow notch.

[2][3][4] Thelymitra gregaria was first formally described in 1988 by David Jones and Mark Clements from a specimen collected near Derrinallum and the description was published in The Orchadian.

[5] The specific epithet (gregaria) is a Latin word meaning "pertaining to a flock or herd" or "common".

The main threats to the species are weed invasion, inappropriate fire regimes and site disturbance.