Euphorbia avasmontana is a robust, cactus-like, many-stemmed succulent, branched from the base and up to 6.6 feet (2 m) tall. The columnar stems are with 5 to 7 ribs, up to 2.8 inches (7 cm) in diameter and grow bunched closely together. The leaves are small and ephemeral, dropping off very soon. The spines are straight, paired and up to 0.8 inches (2 cm) long. Flowering appears in short bags of the yellow cyathia or false flowers.