Chamaerops humilis is a shrub-like clumping palm, with several stems growing from a single base. It has an underground rhizome which produces shoots with palmate, sclerophyllous leaves.
The stems grow slowly and often tightly together, eventually reaching 2–5 m (10–20 ft) tall with a trunk diameter of 20–25 cm (8–10 in). It is a fan palm (Arecaceae tribe Corypheae), and as such, has leaves with petioles terminating in rounded fans of 10–20 leaflets. Each leaf is up to 1.5 m (5 ft) long, with leaflets 50–80 cm (20–30 in) long. The petioles are armed with numerous sharp, needle-like spines; these may protect the stem growing point from browsing animals.
The flowers are borne in dense, short inflorescences at the tops of the stems. The plants usually, but not invariably, are dioecious with male and female flowers on separate plants. The prophyll covers the flowers on the inflorescence until the sexual phase (anthesis) and then splits open apically into two triangular lobes. The number of flowers per inflorescence is highly variable for both male and female plants, depending on the size of the inflorescence. Female flowers are tri-ovulate. Unripe fruits are bright green, turning to dull yellow to brown as they ripen during autumn (September–November). The seed (usually 0.6–0.8 g or 1⁄50–3⁄100 oz) contains a small cylindrical embryo, which is surrounded by several layers, from inner to outer as follows:
- a nutritious endosperm,
- a wide woody layer or endocarp,
- a fleshy and fibrous mesocarp (the pulp), and
- the thin outer layer or exocarp.