A dense, leafy shrub, 1.5–2.0 m tall. Leaves are grey-green, pinnatisect, usually with 3 to 5 lobes cut to the middle of the leaf, and the lobes are long and linear.

Deep yellow flowers are presented in large, showy, flat flower-heads, at branch tips, in summer (October to January). The flower-heads are made up of many small florets packed into rounded discoid heads (i.e. daisy-like flower-heads without the ray petals), that are grouped into simple or compound corymbs (a flat-topped inflorescence where the outer flowers open first).

Athanasia crithmifolia is divided into 2 subspecies, the typical subsp. crithmifolia, and subsp. palmatifida (DC.) Källersjö, which occurs in the southern part of the range and differs in having broadly linear leaf lobes that are palmately cleft in the middle, and the plant is covered in dense, soft, short silky hairs.

Athanasia crithmifolia may be confused with A. trifurcata (trifid-leaf athanasia, coulter bush, klaaslouwbos, kouterbos), and Hymenolepis crithmifolia (also called coulter bush, kouterbos), which flower at the same time.

Athanasia trifurcata has cuneate, usually 3-forked leaves, that are more grey and velvety and not as long and linear as those of A. crithmifolia. It grows on flats and rocky slopes in Namaqualand, through the Western Cape to Port Elizabeth, in the Eastern Cape.

Hymenolepis crithmifolia is a taller shrub, up to 3 m, its leaves longer and more threadlike, and the discoid heads that make up its flower-heads are more loosely clustered and the smaller heads within the compound heads are not as ball-like as they are in the Athanasia heads. It grows on rocky sandstone slopes in Namaqualand and the western part of the Western Cape.