This species usually is a non-forest dweller that occupies open areas such as dry and semi-deciduous forest, grassland savannas, dry woodlands, and cactus and thorn scrub (Jennings et al. 2000). It roosts in caves, buildings, and hollow trees (Marinkelle and Cadena 1972). A large group was flying from riparian forest at dusk, bats appeared in single file, flying about 20 m above ground (LaVal 1977). In Nicaragua, Miller’s mastiff bats have been observed flying over streams, foraging high over trees in a coffee plantation, flying over a concrete water tank, and emerging from a hollow tree over a stream (Jones et al. 1971). In Costa Rica, M. pretiosus was active over a watering hole in a stream (La Val 1977). Eats insects, including beetles and moths. Four individuals had an average of 631 moth scales per gram of faecal material, parts of coleopterans also were present (Freeman 1979).

This species occurs from Guerrero, Oaxaca (Mexico) through Nicaragua, Costa Rica and Panama, and in South America, in Colombia, Venezuela, Guyana, and Brazil (Simmons 2005). In Brazil, it extends to Bahia, Mato Grosso do Sul and Minas Gerais (Nogueira et al. 2008, Claudio et al. 2018). It occurs in lowlands only (Reid 2009).

Recent reports have expanded its known distribution, reaching southern Brazil. Through this wide distribution the species can be found at several protected areas. Given its preference for dry forests and other semi-arid formation, it is important to avoid or reduce habitat loss.