Queensland botanist Les Pedley reclassified the species as Racosperma parramattense in 2003, in his proposal to reclassify almost all Australian members of the genus into the new genus Racosperma, however this name is treated as a synonym of its original name. Along with other bipinnate wattles, Acacia parramattensis is classified in the section Botrycephalae within the subgenus Phyllodineae in the genus Acacia. An analysis of genomic and chloroplast DNA along with morphological characters found that the section is polyphyletic, though the close relationships of many species were unable to be resolved. Acacia parramattensis appears to be most closely related to A. olsenii. Distribution and habitat Acacia parramattensis is found in the Sydney Basin and Blue Mountains in central New South Wales, north to Yengo National Park, west to Grenfell and south to Tumut, from sea level to elevations of . A component of dry sclerophyll forest or woodland, it is found in association with such trees as forest red gum (Eucalyptus tereticornis), Sydney blue gum (E. saligna), mountain white gum (E. dalrympleana), rough-barked apple (Angophora floribunda), turpentine (Syncarpia glomulifera), or in drier locations with gossamer wattle (Acacia floribunda), coast myall (A. binervia), or early green wattle (A. decurrens). A. parramattensis is also a component of the rare and fragmented Southern Highlands Shale Woodlands community. Acacia parramattensis grows on alluvial or shale-based low- to medium-nutrient soil, often with some degree of clay content, or occasionally sandstone-based soils. It is found on lower slopes and along watercourses, as well as ridges. The annual rainfall is over . It has possibly naturalised in Tasmania and other parts of New South Wales. Ecology The bark of A. parramattensis is thin and offers little protection from bushfire, with plants generally perishing from high intensity fires. Most above-ground growth is killed by fire, though plants with trunks thicker than diameter at breast height (dbh) may resprout from epicormic buds. Some plants can survive low intensity fires. Acacia parramattensis has a suckering habit, and can grow from basal shoots after fire, though regeneration is generally by seed after severe fires. The seed has a hard coating and remains in the soil after dropping from the seedpods. It colonises disturbed areas, and the suckers can form groves of plants. The species has a juvenile period of around five years. The seed is consumed by the common bronzewing (Phaps chalcoptera). The foliage serves as food for the caterpillars of