South-eastern Bolivia and central Brazil (southern from Mato Grosso, southern Tocantins, Goiás, and western Minas Gerais), southern throughout Paraguay and Uruguay to north-eastern and central Argentina (south to Río Negro and north-eastern Chubut).
 
Population
Estimated population is unknown (2010).
Screaming Cowbird (Molothrus rufoaxillaris) [XC50803]
by Bernabe Lopez-Lanus from La Rinconada, Saladillo, Buenos Aires, Argentina (song)
Screaming Cowbird (Molothrus rufoaxillaris) [XC49302]
by Rosendo Fraga from Monte Yucat, Cordoba, Argentina (song)
Subspecies
Analyses of mitochondrial DNA indicate closest relationship with Giant Cowbird (Molothrus oryzivorus) and Bronzed Cowbird (Molothrus aeneus).