Coprosma propinqua var. martini is an erect shrub up to 2 m tall whose habitat is under forest, lake margins, tall shrubland on peat, wet seepage with an altitude range of 0–260 m only on Pitt and the Chatham Islands. Its branches are dense and not in a planar arrangement. Branchlets grey-brown, with dense, short, erect to appressed white hairs. The narrowly elliptical leaves are glabrous except for short erect hairs on the upper surface midvein. The leaves are densely arranged on branchlets.

Flowers are unisexual. Male flowers are solitary or in clusters while the female flowers are solitary. Coprosma propinqua var. martinii has didymous (arranged in pairs) white fruit.