[4] The green hylia belongs to the order Passeriformes and the superfamily Sylvioidea, however the classification at family level is under dispute.

The species is often attributed to the family Cettiidae (bush warblers) along with Scotocerca, Erythrocercus, Tesia, Cettia and Abroscopus.

Characteristics shared with sunbirds include a long hyloid with flattened epibranchial horns, a brush-tipped tongue and membrane-covered nostrils.

It is likely that the green hylia, along with other closely related species, have an uncertain position in the phylogenetic tree as a result of rapid radiation of the families within the Sylvioidea.

[11] Analyses of green hylia songs indicated that a build-up of reverberations at the same frequency will lead to longer and louder note tails.

This means that dense vegetation can alter birdsong transmissions to allow for a longer and louder signal, using the same amount of energy for vocalisation.

Since the species uses narrow bandwidth songs they must adjust their frequency relative to influences such as insect vocalisations in order to be heard.

[15] Green hylia habitat includes plant species such as Elaeis guinensis, Celtis zenkeri, Cola gigantea, Acalypha ornata, Markhamia platycalyx, Coffea canephora, Albizia sp., Fagara macrophylla, Funtumia elastica, Pycnanthes angolensis, Musanga cecropioides and Xylopia aethiopica.

[13][14][16] Its diet includes insects, ants or butterflies which are accessible in its feeding area, on the underside of leaves or amongst forest litter.

[5] The nest is built a few feet from the ground in a suitable location, such as the vertical forks of young palm trees.

Nests are crumbly and friable, the bulk being made up of loose tufts of plant matter which are not fragmented, interwoven or compacted.

While the green hylia as a forest generalist is not as sensitive to habitat disruptions as other species, understory and leaf litter clearance does affect its opportunities for foraging and nest building.

The entire forest understory in certain areas is being cleared through slash and burn techniques to make way for the farming of crops such as bananas, maize or beans.