Two skeletons, tracks, faecal pellets, photographs and local reports are described and compared with the few previous records of dwarf Andean deer from Bolivia and Peru. Tarsal bones and incisor teeth were diagnostic traits for Mazama and not for Pudu, while skull measurements, ear shape, body colour and facial patterns were consistent with descriptions of Mazama chunyi. Twenty-five new localities (including more than 60 sites in La Paz and Cochabamba) extended significantly the previously known range for M. chunyi in Bolivia. It occurs in Madidi, Apolobamba, Pilón Lajas, Cotapata, Carrasco and probably Isiboro Sécure protected areas, in habitats ranging from grasslands and Polylepis elfin forests of the ‘ceja de Yungas’ at 3600 m to sub-Andean forests at 1000 m. A geographical information system modelled geographic distribution area based on altitude and ecological zone estimates a potential range of about 45 717 km2 in Bolivia. About 36% of this range (or 41% of the extent of occurrence) is degraded and fragmented, but the rest seems to be in relatively good conservation status. Habitat decline and a limited area of occupancy estimated for Bolivia (and suspected for Peru) suggest that M. chunyi's conservation status should be updated from Data Deficient to Vulnerable VU A4c; B2a+b(iii).