A member of the mamba genus, Dendroaspis, it is slender with dull green upper parts and cream underparts and generally ranges from 1.5 to 2.2 m (4.9 to 7.2 ft) in total length.

Jameson's mamba was first described as Elaps jamesoni in 1843 by Thomas Traill, a Scottish doctor, zoologist and scholar of medical jurisprudence.

[5] In 1848, German naturalist Hermann Schlegel created the genus Dendroaspis, designating Jameson's mamba as the type species.

[7] The genus was misspelt as Dendraspis by French zoologist Auguste Duméril in 1856,[8] and went generally uncorrected by subsequent authors.

[9] In 1936, British biologist Arthur Loveridge described a new subspecies D. jamesoni kaimosae, from a specimen collected from the Kaimosi Forest in western Kenya, observing that it had fewer subcaudal scales and a black (rather than green) tail.

[12] The general consensus is that the sexes are of similar sizes, although fieldwork in southeastern Nigeria found that males were significantly larger than females.

[4] The number and pattern of scales on a snake's body play a key role in the identification and differentiation at the species level.

[12] In West Africa it ranges from Ghana eastwards to Togo, Nigeria, Cameroon, Equatorial Guinea and Gabon.

[12] The subspecies D. jamesoni kaimosae is endemic to East Africa and chiefly found in western Kenya, where its type locality is located, as well as in Uganda, Rwanda, and the adjacent Democratic Republic of the Congo.

Like other mambas it is capable of flattening its neck in mimicry of a cobra when it feels threatened, and its body shape and length give an ability to strike at significant range.

[12][13] In Nigeria males fight each other for access to females (and then breed) over the dry season of December, January and February;[13] mating was recorded in September in the Kakamega Forest in Kenya.

The bulk of its diet is made up of birds and tree-dwelling mammals,[13] such as cisticolas, woodpeckers, doves, squirrels, shrews and mice.

[18] Jameson's mamba is classified as a Snake of Medical Importance in Sub-Saharan Africa by the World Health Organization,[b][19] although there are few records of snakebites.

Systemic effects include generalised swelling, chills, sweating, abdominal pain and vomiting, with subsequent slurred speech, difficulty breathing, and paralysis.

[11] Although cardiotoxins have been isolated in higher proportions from its venom than other mamba species, their role in toxicity is unclear and probably not prominent.

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