The souimanga sunbird was formally described in 1788 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae.

[4][5] The souimanga sunbird is now placed in the large genus Cinnyris that was introduced in 1816 by the French naturalist Georges Cuvier.

There are yellow tufts at the sides of the breast which become visible when the birds lift their wings in courtship display.

Males presumably moult into a duller eclipse plumage by March–April,[9] losing most of the metallic and red feathering for a few months.

Females have grey-brown upperparts, a dull yellow belly and a grey throat and breast with darker markings.

The souimanga sunbird can be found in a variety of habitats from mountain forests to mangroves and scrubland as well as in parks, gardens and other human-modified ecosystems.

Nest-building and incubation of the eggs are done by the female who also plays a greater role than the male in feeding the chicks.