Senecio macrocephalus is a perennial herb which grows up to 0.4 m tall with a stout woody stock. Leaves are mostly in a basal rosette, up to 150 x 30 mm, fleshy, thick-textured and brittle, with a prominent midrib, slightly more white-hairy below than above, margins smooth to shallowly toothed. Multiple flowering stems develop from the base. These stems are almost bare and often branch below the flower heads to produce a group of up to 6 heads. Involucre is glandular-hairy. Flower heads are about 16-28 mm in diameter. Ray florets are bright pink to purplish. Disc florets are white or pink with purple anthers. The fruits are cylindrical and narrow, with a dense pappus. Flowering is from spring to late summer, but in wet seasons it may be found flowering for longer periods.