Despite that several highly disjunct populations of the Scarlet-shouldered Parrotlet are known, the species is currently considered to be monotypic. It is possible that at least some of the apparent gaps in the species’ range are more imagined than real given that all parrotlets of this genus are only infrequently seen, and then usually only in high-altitude flight, making their identification extremely difficult without robust knowledge of their flight-calls. On present knowledge, the Scarlet-shouldered Parrotlet occurs in parts of Venezuela and adjacent northern Guyana, with occasional records on Trinidad, lower Amazonian Brazil (where the species is apparently quite widespread, but its range has only been elucidated in recent decades), northern Bolivia to eastern Ecuador, and eastern Colombia. The Scarlet-shouldered Parrotlet shares the red shoulders with the Red-fronted Parrotlet (Touit costaricensis) of Central America, and the Blue-fronted Parrotlet (Touit dilectissima) of extreme northwest South America, but the red is far more extensive over the wing bend in both of the latter species. The present species is further distinguished by its otherwise extensively blue wings, blue fore-face, largely reddish uppertail (in males), and olive-brown crown and ear coverts.