Spot-tailed Nightjar occurs from southern Mexico south to southern Brazil, but the distribution is discontinuous. It is resident in South America, at least in the majority of its range there, but the isolated populations in Central America apparently are migratory.
In Mexico Spot-tailed Nightjar occurs in southern Veracruz, northern Oaxaca and Chiapas, and Tabasco (Blake 1949, Zimmerman 1957, Howell and Webb 1995, Binford 1989). One series of specimens from Oaxaca reportedly was collected between 1 February and 22 April (Blake 1949), but Binford (1989) questioned these dates, and perhaps the locality, due to documented irregularities in the dates and localites of other specimens from the same collector. Otherwise Spot-tailed Nightjar is present in Mexico from at least late March until July (Howell and Webb 1995). Spot-tailed Nightjar also is reported from northern Honduras, where perhaps it is only a migrant (Monroe 1968), and from northeastern Nicaragua, where it is present at least in March and April, but was not detected in November (Howell 1972).
In Colombia Spot-tailed Nightjar occurs in the northwest from the base of the Serranía de Darién east to the lower Sinú valley, and also at scattered locations in eastern Colombia, east of the Andes (Meyer de Schauensee 1949, Haffer 1975, Hilty and Brown 1986). The distribution extends east across central Venezuela (Phelps and Phelps 1958, Hilty 2003) and northern Guyana, Suriname, and French Guiana (Snyder 1966, Haverschmidt 1968, Tostain et al. 1992). There is a single record for northeastern Ecuador (Ridgely and Greenfield 2001). The distribution in Peru is very discontinuous, with records from the Mayo Valley in San Martín (Begazo et al. 2001), the Gran Pajonal in Junín (Harvey et al. 2011), and the Pampas de Heath, Madre de Dios (Parker et al. 1994). There also is a Whitely specimen from Cosnipata, Cuzco (Salvin and Hartert 1892), although recent surveys of this region failed to detect Spot-tailed Nightjar (Walker et al. 2006).
Spot-tailed Nightjar occurs along the lower Amazon in Pará, Brazil, from just west of the mouth of the Rio Tapajós east to Belem and Marajó (Griscom and Greenway 1941, Blake 1949, Novaes and Lima 1998). This species is widespread across central Bolivia (Remsen and Traylor 1989, Hennessey et al. 2003) and central Brazil, south to central coastal Brazil (Sick 1983). Spot-tailed Nightjar also has been reported at several sites in eastern Paraguay (Lowen et al. 1997, Bodrati and Areta 2010) and in Misiones, Argentina (Bodrati and Areta 2010).
Most populations in South America are assumed to be resident, although Hennessey et al. (2003) describe it as an austral migrant in Bolivia.
The elevational range of Spot-tailed Nightjar is from the lowlands up to 500 m in Mexico (Howell and Webb 1995), to 400 m in Colombia (Hilty and Brown 1986), to 1000 m in Venezuela (Hilty 2003), and up to 1350 m in Peru (Schulenberg et al. 2010).