The mangrove hummingbird was formally described in 1877 by the French ornithologist Étienne Mulsant from a specimen collected by Adolphe Boucard near Puntarenas in Costa Rica.

Both sexes have a medium length bill, slightly decurved, with a black maxilla and a reddish mandible with a dusky tip.

Adult females are similar to males, but with less green on the underparts and grayish tips on the outermost tail feathers.

It inhabits large stands of tea mangrove Pelliciera rhizophorae and sometimes adjacent terrestrial second growth.

It has also been observed feeding at Inga, Heliconia, and Maripa in a terrestrial forest clearing near mangroves.

It builds a cup nest of balsa (Ochroma pyramidale) floss and other soft plant fibers bound with spiderweb and with lichens on the outside.

Its mangrove habitat is continuing to be destroyed for salt evaporation, shrimp farming, charcoal production, and human habitation.