This greenhood has a green and white, striped flower with reddish-brown markings and forms colonies, sometimes of thousands of plants.

They have thread-like ends 20-25 long and between their bases there is a broad, flat sinus with a central notch.

[2][3][4][5] Pterostylis hamiltonii was first formally described in 1810 by William Henry Nicholls and the description was published in The Victorian Naturalist from a specimen collected near Boyup Brook.

[5][6] The red-veined shell orchid is found between Toodyay and the Stirling Range where it usually grows in thickets of Allocasuarina huegeliana on or near granite outcrops in the Avon Wheatbelt, Esperance Plains, Jarrah Forest and Swan Coastal Plain biogeographic regions.

[2][3][4][7] Pterostylis grandiflora is classified as "not threatened" by the Western Australian Government Department of Parks and Wildlife.