The adult male Humblot's sunbird has green upperparts with a dark or gold gloss.

It has yellow pectoral tufts and the lower breast and belly are yellowish green.

The adult female is olive green above, greyer on the head with a brighter rump and greyer underparts with dark spots and streaks, has a white tip to the tail and pectoral tufts.

[3] The song of Humblot's sunbird consists of a series of chipping notes, which are mixed up.

[2] There are two subspecies:[3] The scientific name commemorates the French naturalist Léon Humblot.