The Long-tailed Woodnymph is endemic to the littoral of northeast Brazil, where it is known from the states of Pernambuco, Alagoas, Sergipe, and northernmost Bahia. Although the species remains reasonably common, it is presumably still declining due to ongoing habitat loss, and as a result has been listed as Near Threatened. The Long-tailed Woodnymph is largely restricted to the lowlands, including plantations and parks, but is also found in the highland forests of its range. Like other woodnymphs, this species forages in the understory and middle strata, usually on the periphery of vegetation, taking nectar and occasionally invertebrates. Males defend their territories against conspecifics and other hummingbirds, with breeding documented between November and February, which period appears to the main breeding season for most birds in this region of Brazil.