The red-bellied black snake searches for prey both on land and in water, and is known to climb several feet up trees and shrubs in pursuit of meals. It feeds during the day with a diet consisting of frogs, tadpoles, reptiles, fish, rats, mice and other small mammals, including birds. Though venomous, its bites are rare, as the snake is not aggressive and typically flees at the sight of humans.
Predators of adult snakes include feral cats, falcons and other raptors. Newborn and juvenile red-bellied black snakes may fall victim to frogs, kookaburras, other snakes and the red-backed spider. When fleeing from predators, the species often escapes into the water, as it possesses the ability to remain under the surface for up to 23 minutes.
The snake generally hibernates in underground tunnels and caverns during winter months. Mating occurs in the spring soon after it emerges from its hibernation.