The eastern brown snake is found in most habitats except dense forests, often in farmland and on the outskirts of urban areas, as such places are populated by its main prey, the house mouse.

The International Union for Conservation of Nature classifies the snake as a least-concern species, though its status in New Guinea is unclear.

It is considered the world's second-most venomous land snake after the inland taipan (Oxyuranus microlepidotus), based on its LD50 value (subcutaneous) in mice.

German herpetologist Johann Gustav Fischer described it as Pseudoelaps superciliosus in 1856, from a specimen collected from Sydney.

[18] Within the genus Pseudonaja, the eastern brown snake has the largest diploid number of chromosomes at 38; those of the other species range from 30 to 36.

[20] Wells and C. Ross Wellington described Pseudonaja ohnoi in 1985 from a large specimen from Mount Gillen near Alice Springs, distinguishing it on the basis of scale numbers,[21] but it is not regarded as distinct.

[35] Such areas also provide shelter in the form of rubbish and other cover; the snake can use sheets of corrugated iron or buildings as hiding spots, as well as large rocks, burrows, and cracks in the ground.

[38] At night, it retires to a crack in the soil or burrow that has been used by a house mouse, or (less commonly) skink, rat, or rabbit.

Fieldwork in the Murrumbidgee Irrigation Area found that snakes spent on average 140 days in a burrow over winter, and that most males had entered hibernation by the beginning of May (autumn) while females did not begin till mid-May; the males mostly became active in the first week of September (spring), while the females not until the end of the month.

During a partial display, the snake raises the front part of its body horizontally just off the ground, flattening its neck and sometimes opening its mouth.

In a full display, the snake rises up vertically high off the ground,[43] coiling its neck into an S shape, and opening its mouth.

[44] Due to the snake's height off the ground in full display, the resulting bites are often on the victim's upper thigh.

They noted that snakes were more likely to notice dark clothing and move away early, reducing the chance of a close encounter.

Similarly, walking in undisturbed areas on cool days in September and October (early spring) risked running into courting male snakes that would not notice people until close, as they were preoccupied with mating.

[45] Eastern brown snakes generally mate from early October onwards—during the Southern Hemisphere spring; they are oviparous.

[46] The eggs are laid in a sheltered spot, such as a burrow or hollow inside a tree stump or rotting log.

[25] Eastern brown snakes can reach sexual maturity by 31 months of age,[47] and have been reported to live up to 15 years in captivity.

[53] The eastern brown snake's diet is made up almost wholly of vertebrates, with mammals predominating—particularly the introduced house mouse.

[50] Small lizards such as skinks are more commonly eaten than frogs, as eastern brown snakes generally forage in areas over 100 m (330 ft) distant from water.

[25] Other snakes, such as the common death adder (Acanthophis antarcticus),[55] and carpet python (Morelia spilota), have also been eaten.

[58] Responsible for more deaths from snakebite in Australia than any other species,[59] it is the most commonly encountered dangerous snake in Adelaide, and is also found in Melbourne, Canberra, Sydney, and Brisbane.

[61][c] Clinically, the venom of the eastern brown snake causes venom-induced consumption coagulopathy; a third of cases develop serious systemic envenoming including hypotension and collapse, thrombotic microangiopathy, severe haemorrhage, and cardiac arrest.

[70] The eastern brown snake's venom contains coagulation factors VF5a and VF10, which together form the prothrombinase complex pseutarin-C.[71] This cleaves prothrombin at two sites, converting it to thrombin.

Pseutarin-C is a procoagulant in the laboratory, but ultimately an anticoagulant in snakebite victims, as the prothrombin is used up and coagulopathy and spontaneous bleeding set in.

[73] A 2006 study comparing the venom components of eastern brown snakes from Queensland with those from South Australia found that the former had a stronger procoagulant effect and greater antiplasmin activity of textilinin.

[77] Textilotoxin is a type of phospholipase A2, a group of enzymes with diverse effects that are commonly found in snake venoms.

[78] These are three-finger toxins, a superfamily of proteins found in the venom of many elapid snakes and responsible for neurotoxic effects.

[79] This is thought to be due to the low concentration of the toxin in the venom, which is injected in only small amounts compared with other snake species.

[49] The eastern brown snake is the second-most commonly reported species responsible for envenoming of dogs in New South Wales.

[62] The antivenom had been difficult to research and manufacture as the species was hard to catch, and the amount of venom it produced was generally insufficient for horse immunisation, though these challenges were eventually overcome.