Described by Scottish surgeon and zoologist Andrew Smith in 1849, it has a slender build with a bright green back and green-yellow ventral scales.

In spite of common urban legends and misconceptions labeling the eastern green mamba an aggressive, fast-moving “people-chaser”, it is in fact a shy and elusive species that remains hidden in the trees, and is rarely seen.

Even with its deadly venom, the green mamba has to protect itself from predators, including birds of prey and other snakes, such as cobras.

It has been observed engaging in ambush predation, a trait seen among many Viperidae species, contrary to the active hunting style typical of other Elapidae snakes.

Symptoms of envenomation include swelling of the immediate bite-wound area, dizziness, vertigo and nausea, accompanied by dehydration, labored breathing and difficult swallowing.

The eastern green mamba was first described as Naja angusticeps by Andrew Smith, a Scottish surgeon and zoologist, in 1849, who reported it from Natal and east to Maputo Bay.

[10][11] The British biologist Arthur Loveridge augmented FitzSimons' work with material from outside South Africa, noting some overlap in scalation but supporting the separation.

[15] The eastern green mamba is a large snake, with a slightly compressed and very slender body with a medium to long tapering tail.

Its range extends from Kenya south through Tanzania, Malawi, eastern Zimbabwe and parts of Zambia; it can also be found in Zanzibar and northern Mozambique.

[15][16] An isolated and genetically distinct population is found in South Africa from the extreme northeastern part of Eastern Cape along the KwaZulu-Natal coastline and into southern Mozambique.

As well as wild forest habitats, it is also commonly found in thickets and farm trees such as citrus, mango, coconut, and cashew.

[18] A diurnal species, the eastern green mamba is active by day and sleeps at night coiled up in foliage or rarely a hollow within the trunk or branch.

The study's preliminary evidence shed light on the species' feeding methods, suggesting it may be primarily an ambush predator due to its sit-and-wait behaviour.

Thought to be relatively sedentary, it can remain in the same location for days, apparently moving most commonly to find food or mates.

Gravid females tend to be sedentary, but males actively seek and court prospective mates during the rainy season between April and June.

Typically, one male initiates a fight by moving on top of the other's body and tongue-flicking, after which the two entwine and push, attempt to pin the other's head to the ground.

Documented prey include the sombre greenbul, which occur in dense areas of natural and cultivated vegetation along Kenya's coastline.

[31] The average dose able to kill a human is about 18–20 mg.[32] In 2024, Youtuber Graham ‘Dingo’ Dinkelman dies after he was bitten by the Eastern green mamba that eventually led to him in induced coma following anaphylactic shock.

[33] Symptoms of envenomation by this species include pain and swelling of the bite site, which can progress to local necrosis or gangrene.

[28] Another prominent component is a group of proteins known as dendrotoxins; although structurally homologous to Kunitz-type protease inhibitors, they block voltage-dependent potassium channels, stimulating the release of acetylcholine and causing an excitatory effect.

[14] Standard first aid treatment for any bite from a snake suspected to be venomous is the application of a pressure bandage, minimisation of the victim's movement, and rapid conveyance to a hospital or clinic.

[38] A polyvalent antivenom produced by the South African Institute for Medical Research is used to treat eastern green mamba bites.

Large concentrations of two to three individuals per hectare have been documented in coastal Kenya and southern Tanzania, and in one instance a group of five were seen in a single tree.