The green tree python is characterized by a relatively slim body. The relatively long tail accounts for about 14% of the total length. The head is large and clearly defined from the neck. The muzzle is large and angular. The body is triangular in cross section with a visible spine. The species usually reaches a total length of 150-180 cm (4.9-5.9 ft), but large females may reach 200 cm (6.6 ft). The size also varies depending on the region of origin.

They are found in Indonesia (Misool, Salawati, Aru Islands, Schouten Islands, most of Western New Guinea), Papua New Guinea (including nearby islands from sea level to 1,800 m elevation, Normanby Island and the d'Entrecasteaux Islands) and Australia (Queensland along the east coast of the Cape York Peninsula).

Its main habitat is in rainforests, bushes, shrubs and trees. The largest threat to the species is habitat destruction due to logging of forests.

Primarily arboreal, these snakes have a particular way of resting in the branches of trees; they loop a coil or two over the branches in a saddle position and place their head in the middle. This trait is shared with the emerald tree boa, Corallus caninus, of South America. This habit, along with their appearance, has caused people to confuse the two species when seen outside their natural habitat.

The diet consists mostly of small mammals, such as rodents, and sometimes reptiles. This snake, like the emerald tree boa, was thought to eat birds; however, Switak conducted field work on this issue. In examining stomach contents of more than 1,000 animals, he did not find any evidence of avian prey. Prey is captured by holding onto a branch using the prehensile tail and striking out from an s-shaped position and constricting the prey.