The Sierra Box Turtle, Terrapene nelsoni, comprises 2 recognized subspecies that are distributed across the Sierra Madre Occidental mountain chain in western Mexico and little is known about their natural history. We present new information on the natural history of Terrapene nelsoni klauberi. Our study area was the Monte Mojino reserve located within the larger Sierra de Alamos–Río Cuchujaqui federal protected area in southeastern Sonora. We located 49 individuals in 3 different vegetation types: 4 were found at 600 m above sea level (masl) in the tropical dry forest, 4 at 1000 masl in grassy oak (Quercus spp.) savannah, and 41 at 1300 masl in pine(Pinus spp.)–oak forest. Seven turtles were monitored using radiotelemetry and have the average home range size of 1.7 ha. The areas we sampled appear to consist of mainly adults and the sex ratio is female-biased (1♂:1.5♀). Cloacal temperatures of active turtles and their immediate surroundings suggest that T. n. klauberi actively maintain their body temperature above the surrounding temperatures. Males also have higher average body temperatures than females (29.58°C ± 2.26°C vs. 27.35°C ± 2.71°C). We found no significant patterns of sexual dimorphism in carapace length (i.e., sexual size dimorphism) but did find sexual dimorphism in head size. We also found that 44% of males and 22% of females had severe damage to their marginal scutes, possibly from a local predator or from enduring bites over time from other turtles. Lastly, we observed T. n. klauberi foraging on beetles, mushrooms, grass, and wildflowers. These findings provide a first insight into the natural history of T. n. klauberi and how this species is distributed across different elevations and vegetation types. This information provides a starting point to assess the conservation status of this species. However, this species remains unstudied throughout the rest of its geographic range.