Typically found at elevations above 1,800 m (5,900 ft), the mountain blackeye sometimes moves to lower altitudes during periods of drought.

It feeds on insects, nectar, pollen, and small fruits, and is a major pollinator of several species of Rhododendron.

The female lays a single egg, and the nestling takes 14–15 days to fledge after hatching.

Richard Bowdler Sharpe first described the mountain blackeye in 1888, using a specimen collected on Mount Kinabalu in northern Borneo.

[2] It remained in that genus for more than a century, with its affinities to other members of Zosteropidae (white-eye) family unclear.

[5] Mitochondrial DNA studies have shown that the species divides neatly into two clades, one in Sabah and the other in Sarawak.

[9] Researchers theorize that the subspecies that make up the two clades were separated by glacial events, diverging as long ago as the mid-Pleistocene.

[10] The adult of the nominate race, emiliae, is dark olive-green on the head and upperparts with a blackish tinge to the green, particularly on the crown.

The subspecies fusciceps is smaller and relatively shorter-tailed than emiliae, with a sepia tint to its crown and forehead.

[1][14] Its habitats include primary upper montane forest, summit scrub, and gully vegetation.

[1] The mountain blackeye feeds on nectar, pollen, insects (particularly caterpillars, grasshoppers and beetles), and small berries, including raspberries.

[22] Because the waxy secretions are produced year-round, they can be an important food source for mountain blackeyes when other plants are not in flower, or when insects are hard to find.

[10] The nest is a shallow cup made of rootlets and dried grass, and lined with the sporophyte stalks or setae of mosses.

It measures roughly 7.5 cm (3.0 in) across and is typically built in the fork of a branch of a Leptospermum tree within 1 to 8 m (3 to 26 ft) of the ground.

Its overall population size has not been quantified, but it is thought to be declining, primarily due to habitat destruction and fragmentation.

[25] However, protection does not necessarily forestall habitat destruction, as for example, permission has been granted for extensive logging in the forest reserve on Mount Trus Madi.