Argentina, Aruba, Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Netherlands Antilles, Paraguay, Peru, Suriname, Trinidad and Tobago, Uruguay (B), Venezuela.
Breeds eastern and south-eastern Bolivia, Paraguay, southern Brazil (Sío Paulo south to Rio Grande do Sul), north-eastern Argentina (south to Buenos Aires) and Uruguay. Migrates north to Amazon Basin and as far as north-eastern Colombia, northern Venezuela, Netherlands Antilles, Trinidad and the Guianas.
 
Population
Estimated population is unknown (2010).
Small-billed Elaenia (Elaenia parvirostris) [XC434819]
by Rosendo Fraga from Las Lajas, Catamarca, Argentina (song)
Small-billed Elaenia (Elaenia parvirostris) [XC687750]
by Niels Krabbe from Santiago del Estero: Destacamento Aybal, PN Copo, Argentina (call)
Subspecies
Described taxon Elaenia aenigma is a synonym for this species. Closely related to White-crested Elaenia (Elaenia albiceps), and vocalizations are very similar. It has been suggested that they are conspecific, but apparently do not hybridize across a broad area of range overlap in Argentina, although hybridization does occur in a narrow area of overlap in southern Bolivia. Reported hybridization with Olivaceous Elaenia (Elaenia mesoleuca) in south-eastern Brazil (Rio Grande do Sul) is disputed by some authors.