Fawn-breasted Brilliant is resident in the Andes of Colombia, Ecuador, and Peru. In Colombia, Fawn-breasted Brilliant occurs on the west slope of the Eastern Andes, south to the head of the Magdalena Valley; on both slopes of the Central Andes; and locally on the west slope of the Western Andes (Meyer de Schauensee 1949, Hilty and Brown 1986, Salaman and Mazariegos 1998).
It is more continuously distributed along both slopes of the Andes of Ecuador, on the west slope from Pichincha south to El Oro and western Loja, and along the entire eastern slope, although the distribution apparently is more local in southeastern Ecuador (Rasmussen et al. 1996, Ridgely and Greenfield 2001a). The distribution of Fawn-breasted Brilliant is continuous along the east slope of the Andes of Peru south to the Cosñipata valley in Cuzco (Zimmer 1951, Walker et al. 2006, Schulenberg et al. 2010).
The elevational range of Fawn-breasted Brilliant in Colombia is 1800-2600 m (but possibly to as low as 1000 m in the Magdalena Valley; Hilty and Brown 1986); from 1100-2100 m in Ecuador, but locally to as high as 2400 m (Ridgely and Greenfield 2001a); and from 1500-1500 m in Peru (Schulenberg et al. 2010).