Acacia cockertoniana Maslin, a new species with a restricted distribution in the south-west arid zone of Western Australia is described. The species is restricted to banded ironstone ranges which accounts for its discontinuous distribution between Mt Jackson (130 km north of Southern Cross) and near Mt Magnet (c. 270 km north-west of Mt Jackson). Sterile specimens from north of Mt Magnet require confirmation as being this species. Acacia cockertoniana is often abundant in the places where it occurs and current evidence suggests that it is most common in the vicinity of the Windarling Range. Acacia cockertoniana appears to be most closely related to A. balsamea Cowan & Maslin.