The Boomslang is largely tree-living but may descend to the ground to bask. In trees it poses no threat to humans as it is extremely reluctant to bite and bites are rare. It is a popular fallacy that being back-fanged it can only bite onto a small digit – this is incorrect as it can open its mouth very wide.

Hatchlings and juveniles are grey with a massive emerald green eye but change to the adult colours around 1 m. Most males are bright green, sometimes with black between the scales but in the Cape Provinces they are usually black above with green, yellow or orange sides. Females are brown in colour.

Boomslang venom is haemotoxic and compromises the blood clotting mechanism, causing uncontrolled bleeding if not treated. The South African Vaccine Producers manufacture a monovalent antivenom for Boomslang bites that is very effective.