Historically, mule deer (Odocoileus hemionus) had a distribution area as large as the Chihuahuan Desert in Mexico, but in recent years, its populations have decreased and distribution areas have become isolated. This species exhibits a high degree of intraspecific variation in its use of habitat resources and home range size. In the Mapimí Biosphere Reserve, where the southernmost population of mule deer is located, over the course of 3 years, 7 females and 1 young male mule deer were monitored using radiotelemetry. Based on the deer location data, home range and habitat use were estimated for each deer. The mean (± SD) home range size for females was 14.70 km² (± 5.89), the home range of the male was 18.05 km². These estimates are among the smallest reported for the species. During the dry season, the use of certain topographic characteristics of the habitat was more similar among the individual deer than it was during the rainy season. The group of deer we sampled did not show preference for any particular type of vegetation, but rather used the majority of plant associations, depending on their availability. Preference was only exhibited by individual deer. The young male made use of the habitat similar to that of most of the females.