This greenhood was first formally described in 2016 by David Jones and Lachlan Copeland and given the name Diplodium divaricatum. The description was published in the Australian Orchid Review from a specimen collected on Mount Duval. In the same year, the same authorities changed the name to Pterostylis divaricata to allow for the different taxonomic views held at generic level within the subtribe. The specific epithet (divaricata) is a Latin word meaning spread apart, referring to the spread tips of the lateral sepals.