The Red-capped Myzomela has been recorded in varied habitats on Bougainville, from coastal areas to high elevations. Some sources call Myzomela lafargei the Scarlet-naped Myzomela.
The species is mostly yellow. Males have a black head, back, tail and shoulders, yellow-edged wings, and a variable red cap. Females are plain, dull yellow.
It occurs in forest and scrub. The Bougainville survey recorded the species across varied settings from coastal areas to high elevations.
An extinction-risk assessment has not been added yet.