This species is about 12 cm long with rounded wings, strong legs, and a conspicuous ring of white feathers round the eyes. The upper parts are green, and the throat and vent are bright yellow. The members of the nominate group have a pale yellow central belly with peach colored flanks. The members of the capensis subgroup have a grey breast and belly, while the virens subgroup have a greenish-yellow breast and belly.
Feeds mainly on insects, but also soft fleshy flowers, nectar, fruit and small grains. It will come to bird feeders.
Breeding season is September to December. Builds a cup nest in a tree, lays 2-3 pale blue eggs, which hatch in 11-12 days. Young fledge in 12-13 days.
Cape white-eyes are expected to live an average of 8 years in the wild. Captive birds are expected to live 10 years. This short lifespan likely correlates with rapid reproduction rates.