[9] The nominate subspecies of white-bellied emerald is found on the Caribbean slope from the Mexican states of Chiapas, Tabasco, and Yucatán south through Belize, Guatemala, and Honduras into Nicaragua.

C. c. genini is found in southeastern Mexico north of the nominate between San Luis Potosi and northern Oaxaca.

C. c. pacifica is found in extreme southern Chiapas on the Pacific slope of Mexico and disjuctly in Guatemala.

Its principal diet is nectar taken from a wide variety of flowering plants, and it also seeks insect prey in foliage.

However, in 2019 a pair of researchers documented a female white-bellied emerald feeding a juvenile rufous-tailed hummingbird.

Females build a cup nest on a horizontal branch, using plant material and cobweb decorated on the outside with lichen and moss.

Its calls are "mostly rolled or trilled chips, trirr and ti-ti or tsi-tsir, and longer drii-i-i-it and tsi si-si-si-sit, etc.