Pimelea petrophila is an erect, dioecious shrub that typically grows to a height of and has its young stems covered with short, fine hairs. The leaves are arranged in opposite pairs, elliptic to narrowly elliptic, long, wide and usually
glabrous. The flowers are arranged in clusters of many white flowers, surrounded by 2 to 4 leaf-like involucral bracts long, wide and usually longer than the male flowers. The
floral tube of male flowers is long, the
sepals long, the floral tube of female flowers is long with sepals long. Flowering mainly occurs from July to October. This pimelea is similar to
P. flava but has seeds with a pitted (
foveate) surface, whereas those of
P. flava are furrowed. ==Taxonomy and naming==