The green honeycreeper is 13–14 cm (5.1–5.5 in) long and weighs 14 to 23 grams (0.49 to 0.81 oz), averaging about 19 grams (0.67 oz). It has a long decurved bill. The male is mainly blue-tinged green with a black head and a mostly bright yellow bill. The female green honeycreeper is grass-green, paler on the throat, and lacks the male's iridescence and black head. Immatures are plumaged similar to females. The call is a sharp chip.
This is a forest canopy species. The female green honeycreeper builds a small cup nest in a tree, and incubates the clutch of two brown-blotched white eggs for 13 days. It is less heavily dependent on nectar than the other honeycreepers, fruit and seeds being its main food (60%), with nectar (20%) and insects (15%) as less important components of its diet.