Few nests of Black-bellied Hummingbird are reported. In Costa Rica, breeding is from October to March, but sometimes is initiated as early as July (Skutch 1967, Stiles 1985, Stiles and Skutch 1989). Breeding is closely correlated with the abundance of canopy flowers (especially of the epiphytes Cavendishia quereme and Thibaudia costaricensis and the treelet Cephaelis elata) (Stiles 1985).
The nest is a cup composed of tree fern scales and spiderweb, sparsely decorated with bits of moss and lichen. The nest is 2-4 m above the ground, in forest understory or at forest edge, and often is placed beneath large, overhanging leaves. The clutch is two; the eggs are white and unmarked (Skutch 1967, Stiles and Skutch 1989).