Close study of the widely-distributed southwestern Western Australian Hibbertia acerosa (R.Br. ex DC.) Benth. (Dilleniaceae) has revealed that it comprises four distinct, parapatric or narrowly sympatric species differing in leaf morphology, sepal indumentum and floral bract shape. One of the segregate species has an earlier name in Pleurandra, which is recombined here as Hibbertia juniperina (Turcz.) K.R.Thiele. The new species H. simkiniae K.R.Thiele and H. callida K.R.Thiele are described, the former for a relatively restricted species occurring inland of Kalbarri and the latter for the most widespread segregate from H. acerosa sens. lat. The true H. acerosa sens. str. is redescribed to account for its narrower circumscription, and a key and distribution maps provided for all taxa.