Yellow-bellied Seedeaters are common residents of grassland and agricultural areas from Costa Rica south to Brazil, although they are absent from much of the Amazon Basin. The name Yellow-bellied Seedeater is slightly misleading as even the mostly brightly colored males have only pale yellow underparts. More characteristic of the male is the black hood and olive upperparts. During the breeding season males hold territories and sing perches on the tops of shrubs and trees. When not breeding, Yellow-bellied Seedeaters gather in mixed flocks and forage for seeds with other species of seedeaters and grassquits.
In the Caribbean, Yellow-bellied Seedeaters are uncommon and local breeding residents on the southern islands of Grenada, Carriacou and the Grenadines from March to November. It is considered a vagrant on St. Vincent. Outside the breeding season it is likely these Caribbean populations migrate south to South America and Costa Rica where they are more common.