Common in woodlands, forests, swamplands, along river banks and waterways, the red-bellied black snake often ventures into nearby urban areas.

The red-bellied black snake was first described and named by English naturalist George Shaw in Zoology of New Holland (1794) as Coluber porphyriacus.

Juveniles are similar to the eastern small-eyed snake (Cryptophis nigrescens), with which they can be easily confused, although the latter species lacks the red flanks.

[23] Other similar species include the blue-bellied black snake (Pseudechis guttatus) and copperheads of the genus Austrelaps.

[20] It can be found in the urban forest, woodland, plains, and bushland areas of the Blue Mountains, Canberra, Sydney, Brisbane, Melbourne, Cairns, and Adelaide.

[20] The red-bellied black snake is most commonly seen close to dams, streams, billabongs, and other bodies of water,[20] although they can venture up to 100 m (350 ft) away,[31] including into nearby backyards.

[33] Red-bellied black snakes can hide in many places in their habitat, including logs, old mammal burrows, and grass tussocks.

A 1987 field study in three New South Wales localities found that these areas vary widely, from 0.02 to 40 ha (0.05 to 100 acres) in size.

[35] If provoked, it recoils into a striking stance as a threat, holding its head and front part of its body horizontally above the ground and widening and flattening its neck.

[36] Rather than entering true hibernation, red-bellied black snakes become relatively inactive over winter, retreating to cover and at times emerging on warm, sunny days.

[38] Groups of up to six hibernating red-bellied black snakes have been recorded from under concrete slabs around Mount Druitt and Rooty Hill in western Sydney.

[39] Males are more active in the Southern Hemisphere spring (early October to November) as they roam looking for mates; one reportedly travelled 1,220 m (0.76 mi) in a day.

They wrestle vigorously, but rarely bite, and engage in head-pushing contests, where each snake tries to push his opponent's head downward with his chin.

[40] The male seeks out a female and rubs his chin on her body, and may twitch, hiss, and rarely bite as he becomes aroused.

The red-bellied black snake is ovoviviparous; that is, it gives birth to live young in individual membranous sacs,[20] after 14 weeks' gestation,[35] usually in February or March.

[44] The diet of red-bellied black snakes primarily consists of frogs, but they also prey on reptiles and small mammals.

[20] As red-bellied black snakes grow and mature, they continue to eat the same size prey, but add larger animals, as well.

[45] Although they prefer live food, red-bellied black snakes have been reported eating frogs squashed by cars.

[46] The introduction of cane toads in Australia dates to 1935, when they were introduced in an attempt at biological control of native beetles, which were damaging sugarcane fields (a non-native plant).

[53] Symptoms of systemic envenomation—including nausea, vomiting, headache, abdominal pain, diarrhoea, or excessive sweating—were thought to be rare, but a 2010 review found they occurred in most bite victims.

Patients may suffer a loss of sense of smell (anosmia);[54] this is unrelated to the severity of the envenoming and can be temporary or permanent.

[52] Although the venom contains the three-finger toxin α-elapitoxin-Ppr1, which acts as a neurotoxin in laboratory experiments, neurotoxic symptoms are generally absent in clinical cases.

[58] In 2006, a 12-year-old golden retriever suffered rhabdomyolysis and acute kidney injury secondary to a red-bellied black snake bite.