Sooty Swift primarily occurs in eastern Brazil, as well as in adjacent northeastern Argentina (Missiones) and eastern Paraguay (Sick 1993, Brooks et al. 1995, Chantler 2000, Guayra Paraguay 2004, Pearman et al. 2010). Breeding of Sooty Swift is confirmed from Tocantins, Minais Gerais, Rio de Janeiro, and Paraná in Brazil (Vasconcelos et al. 2006, Biancalana et al. 2012) and from Misiones, Argentina (Pearman et al. 2010). At least in the southern portion of its range, Sooty Swift may be present only seasonally, e.g. primarily present September-March in Rio Grande do Sul, Brazil (Belton 1984) and August-March in Misiones, Argentina (Pearman et al. 2010). Until recently Sooty Swift was considered to be primarily a bird of coastal southeastern Brazil, but it now is reported north to Ceará , Bahia, and Tocantins in northeastern Brazil (Albano and Girão 2008, Biancalana et al. 2012).
Although sometimes reported from Bolivia, for example (e.g. Chantler 2000), there are no confirmed records from that country (Hennessey et al. 2003, Pearman et al. 2010).
The elevational range of Sooty Swift reportedly is from 700-2100 m (Parker et al. 1996).