Recent and historical data suggest that Mazama nana is associated to the Araucaria moist forests (Mixed Ombrophilous Forest) and its ecotones with the adjacent ecoregions: Paraná-Paraíba interior forests (Semideciduous Seasonal Forests); Serra do Mar coastal forests (Ombrophilous Dense Forest) and Cerrado (Abril et al. 2010). Some authors mention its preference for mountainous habitats (Cabrera and Yepes 1960, Duarte 1996, Di Bitetti et al. 2008), but presence in plain and soft hilly landforms is common throughout its distribution.

Brazilian Dwarf Brocket is sympatric with other Mazama species, at least along its ecotonal areas. In Paraguay, Argentina and the western parts of Brazil, this species appears to be partially segregated of M. americana by using habitats with dense lower strata, abundant bamboo understory and secondary growth forests (Chebez and Varela 2001, Vogliotti 2008).

There is no specific information about its spatial, behavioural or feeding ecology, which are probably similar to the general pattern of Mazama, including: nocturnal, solitary, territorial and sedentary habits on small home ranges (Abril et al. 2010).

Small subpopulations still persists in forest remnants among agricultural landscapes where they are subject to population decline, extinction and recolonization processes. Non-invasive studies using faecal DNA markers are in course to access initial information on population ecology of M. nana in protected or fragmented areas in Brazil.

Known from a small sample of specimens in museums, this species was formerly included within the Little Dwarf Brocket, Mazama rufina (Redford and Eisenberg 1992). For Redford and Eisenberg (1992) and Eisenberg and Redford (1999) this species occurs in southeast Paraguay, north of Misiones Province in Argentina, and in the Brazilian states of Minas Gerais (extreme south), São Paulo (except Serra do Mar), Mato Grosso do Sul (south and southeast), Paraná, Santa Catarina and Rio Grande do Sul (north). However, this distribution is not consistent with the origin of scarce material in the Brazilian scientific collections that restrict its distribution to the southwest of Sao Paulo (to the south of Paranapanema River), Parana, Santa Catarina and north of Rio Grande do Sul (Rossi 2000).

The loss of preferential habitats could have caused the occupation of forest formations less preferred by the species. This would explain the recent records in the east of Parana and Santa Catarina (Montane Forest and Submontane Ombrophilous Dense Forest; Margarido and Braga 2004, J.M.B. Duarte pers. comm.) and the absence of historical records in these regions (Rossi 2000).

The National Museum of Natural History of Paraguay has records of M. nana in San Rafael National Park region (Gamarra de Fox and Martin 1996) and in Argentina, this species may be found in almost all the remaining natural forests of Misiones Province (D.M. Varella pers. comm.).

In Brazil with respect to protected areas, this species is mentioned in some national parks (Iguaçu, Araucárias, Serra do Itajaí), state parks (Lauraceas, Pau Oco, Boguaçu, Vila do Espírito Santo, São Camilo), private reserves of the natural patrimony (Federal das Araucárias, Monte Alegre Farm) and Mata Preta Ecological Station (J.M.B. Duarte and M.L. Oliveira pers. comm.). In Misiones, Argentina, many conservation units shelter important subpopulations of this species, such as the Iguaçu National Park and the State Parks of Urugua-í, Foerster, Piñalito, Cruce Caballero, Esmeralda, Moconá and Cuña Pirú (D.M. Varela pers. comm.). In Paraguay, the majority of the Atlantic Forest habitats are extinct, what remains is in protected areas such as Reserva Natural del Bosque Mbaracayú and the Itaipu Hydroelectric Power Plant Reserve. Currently, San Rafael National Park, which has records of the species, suffers many pressures and threats (J.L. Cartes pers. comm.).

In Brazil this species have been included in the State Red Lists to improve the local conservation actions (Duarte et al. 2012). The National Agency for Biodiversity Conservation (ICMBio) has developed a National Conservation Action Plan (PAN) for deer species to implement conservation actions for endangered Brazilian species in terms of public policies, research priorities and population management. In Argentina, M. nana is considered to be Vulnerable although the subpopulations of Misiones Province seem to be stable (Diaz and Ojeda 2000).