Haemanthus sanguineus is a winter-growing, deciduous bulb and reaches a height of 300 mm when flowering. This species has an egg-shaped bulb, 40–100 mm in diameter, that is covered in thinly layered, white to yellow scales. Each bulb produces 2 leathery green leaves, 80–400 mm long, often with red, cartilaginous margins. The leaves are circular to broadly oblong and usually lie flat on the ground, just above the surface of the soil.

Haemanthus sanguineus has a rounded, pink to red inflorescence on a plain red peduncle, which protrudes before the leaves emerge. This inflorescence appears in late summer to autumn (from January to April) and consists of many flowers crowded into a dense head, surrounded by leathery floral bracts. The stamens are well exserted and carry yellow pollen. Fleshy pink or red berries follow the flowers, holding a few reddish-brown, egg-shaped seeds.

Haemanthus sanguineus is often mistaken for H. coccineus, but the latter species does not have a leathery leaf margin and it has a spotted peduncle. Also, the floral bracts of H. sanguineus are smaller so that the flowers stick out above them, whereas those of H. coccineus are larger and cover the flowers.