The pygmy mulga monitor is arboreal, with a prehensile tail. It grows to a total length of around 40 cm (16 inches). The upper surface is brown, grading to grey at the sides. V. gilleni weighs, on average, 60–80 grams (2.1–2.8 oz). Males and females can be distinguished by the presence of spines on the sides of the male's vent.
It is particularly well adapted to arid conditions, losing water at half the rate of other Australian monitor species.
Although arboreal, much of their prey is found by foraging on the ground. They primarily eat spiders, beetles, other lizards, geckos, and a variety of insects.
Ritualized fighting sometimes occurs between males. Unlike larger monitors, which grapple with each other while standing on their hindlegs, they grapple each other with all 4 limbs, belly to belly, and roll around on the ground trying to force the other onto its back. Biting may also occur.