Body length from nose to the base of the tail is about 95 mm (about 4 inches).

Tail is tapered and cylindrical, and longer than the body.

Geckos can be distinguished from other lizards by their flattened heads, swollen at the temples, and their minute body scales.

The skin of Naultinus grayii is bright green, and many individuals have white or yellow blotches on the back and legs.

This species also has a blue-lined mouth and a red tongue.

Geckos are said to have no eyelids, but their eyelids are transparent and fused in the closed position to form a protective screen. The eye screen is cleaned with the tongue.

In tree geckos, the toes are elongated and curved claws help to grasp branches. However, their toes still have the rows of microscopic scales that help other geckos cling to smooth surfaces.

They can shed their tails if grasped, although arboreal geckos seem to do so reluctantly. The tail is somewhat prehensile and is useful in climbing. .

Geckos have well-developed vocal cords and can communicate both by barking or chirping and by clicking their tongues against the roof of the mouth.

Geckos can reproduce by parthenogenesis (without fertilization) if males are absent. Like other New Zealand geckos, the Northland Green Gecko bears live young, retaining its eggs until the babies have emerged.

Usually two babies are born, and are large -- nearly half the size of the mother. The gestation period is uncertain, as females can retain sperm for an extended period of time before the eggs are fertilized. However most babies are born around April. This species has been successfully bred in captivity.

They feed by creeping up on their insect prey and making a quick grab with their large mouths. Their teeth are small and probably used more for holding on to their prey than for chewing it. In their natural environment, their only serious predators are birds, especially kingfishers. However, introduced predators like cats and rats are a danger to them. Because they are extremely attractive little animals they are also subject to poaching and smuggling.

Like other reptiles, geckos shed their skins, but all in one piece, as a snake does. New Zealand geckos have long lifespans, reaching into several decades for captive animals.