The White-crested Elaenia is resident in the Andes of southwestern Colombia south, along both slopes of the Andes in Ecuador and to the west slope of the Andes in northwestern Peru (griseogularis); resident in the Andes of central Peru, on both slopes (Pacific slope, and in the Marañón valley) of the Western Andes, and on the western (Marañón valley) slopes of the eastern Andes (diversa); resident in the Andes of southern Peru in Cuzco (urubambae), and along the east slope of the Andes in southern Peru and in northwestern Bolivia (albiceps).
Subspecies chilensis breeds from southern Bolivia south to the Andes of northwestern Argentina, and then south at lower elevations through Argentina to Tierra del Fuego. Also breeds in central and southern Chile. Chilensis is almost completely migratory. It arrives in Chile in September; it departs the breeding range by March or early April. The non-breeding distribution of White-crested Elaenia still is not known completely. Chilensis occurs as a non-breeder along the east slope of the Andes north at least to northern Peru (and possibly to Ecuador or even to Colombia), overlapping with the resident taxa griseogularis, diversa, urubambae and albiceps, and also with the migratory modesta. Chilensis also occurs as a non-breeder in northeastern Brazil. There are also are a few specimen records from sites in the central Amazon basin, although there are few or no recent records from this region, and its status there is not clear.
Subspecies modesta breeds (November –June) near the coast, and on the western slopes of the Andes (up to 1600 m), in western Peru, from La Libertad south to extreme northern Chile. Most of the population migrates east across the Andes and winters (June-December) along the east slope of the Andes of Peru from San Martín south to Madre de Dios. In southern Peru and in northern Chile, at least some individuals may be found year round, although it is not known if these are resident individuals, or whether local breeders migrate away and are replaced by birds from another population.
Vagrant to the Falkland Islands. A White-crested Elaenia, identified as chilensis, also was seen (and photographed) in South Texas (USA) from 9-10 February 2008 (Reid and Jones 2009).