Victorian state botanist Ferdinand von Mueller first recounted "Banksia blechnifolia" in 1864, from material collected in 1861 by a G. Maxwell. The species name is derived from "Blechnum", a genus of fern, and "folium" "leaf", hence "fern-leaved". Von Mueller held it to be close to , but in his 1870 arrangement, English botanist George Bentham regarded it as synonymous with that species. Von Mueller wrote of it again in 1869 as a variety of "B. repens", giving it the name "Banksia pinnatisecta". The species was then mostly forgotten until 1931, when it was collected again by Western Australian botanists William Blackall and Charles Gardner near Middle Mount Barren. As the region was opened up to agriculture, the species was collected more often during the following decades. It was informally known as "Banksia" sp. "Lake King" during this time and was brought into cultivation. No subspecies are recognized.