Eastern Paraguay, south-eastern Brazil (southern from south-eastern Bahia and southern Espírito Santo), north-eastern Argentina (south to eastern Santa Fe, Entre Ríos and northern Buenos Aires) and Uruguay.
 
Population
Estimated population is unknown (2010).
Spix's Spinetail (Synallaxis) [XC332912]
by Jerome Fischer from Itatiaia National Park - Agulhas Negras road, Brazil (song)
Spix's Spinetail (Synallaxis spixi) [XC352262]
by Marcelo Jordani Feliti from Parna Capara\u00f3, Alto Capara\u00f3, Minas Gerais, Brazil (song)
Subspecies
No subspecies.
Close relationship to Pale-breasted Spinetail (Synallaxis albescens) and Dark-breasted Spinetail (Synallaxis albigularis) suggested by plumage and vocal similarities. In the past was considered conspecific with Cinereous-breasted Spinetail (Synallaxis hypospodia). The two are thought to be possibly sister-species by some authors, but others consider them not closely related because of differences in tail morphology, throat pattern and voice.