The Green-breasted Mango Hummingbird measures between 10.2 and 12 cm in length. Males weigh an average of 7.5 g, while females weigh 6.8 g. Its beak, measuring 25 mm long, is slightly curved.
The male has a shiny, lustrous green back. The crown and the center of the chest are matte black, bordered by bluish-green. The flanks are bright green, and the black on the chest narrows down towards the belly. It has white tufts on its thighs, and the outer tail feathers are wine to magenta-colored with black tips.
This hummingbird is a common resident in various habitats, including areas with broadleaf trees between 10 and 60 meters tall, shrublands with scattered trees, open savannas, secondary forests, gallery forests, mangroves, and forest edges.
It feeds on flower nectar and insects. It visits the flowers of trees such as legumes (especially Inga, Caesalpinia, and Erythrina), as well as those of the genus Ceiba and vines. Additionally, it captures insects in flight at considerable heights.