A common blue-headed sunbird of montane forests and forest edges, rarely found in lower-elevation foothills. Uniformly yellow-green body starkly contrasts with a dark purple-blue or green-blue iridescent head. Bill is relatively long with a noticeable curve. Visually similar to other “hooded” sunbirds, most notably Green-headed Sunbird, but Cameroon Sunbird has a uniformly colored body and a darker hood. Vocalizations include a sequence of rapid, well spaced whistles “tiu tiu tiwu tiwu tiu tiu” of variable length and pitch, rapid jumbles of mechanical whistles on varying pitches, and individual sharp “tiu!” and “tik!” calls.