Pachypodium namaquanum is an usually single-stemmed, succulent plant or small tree, growing extremely slowly with stem up to 10 inches (25 cm) in diameter and up to 8.2 feet (2.5 m) tall.
The stems are cylindrical, mostly unbranched, covered with warty tubercles from which sharp spines protrude in a slightly downward direction.
The leaves form a crowded rosette at the apex of the trunk. They are simple, obovate to oblong, green-grey and densely velvety on both surfaces.
The flowers are tubular, red on the inside and yellow-green outside, up to 2 inches (5 cm) long and up to 0.4 inch (1 cm) across at the mouth. The fruits are horn-like with twin pencil-thin tapering capsules of up to 2 inches (5 cm) long.