<p>Changes in the Earth’s climatic conditions influence the geographic distributions of species, resulting in variations in patterns of diversity and occurrence across space and time. Because of their high specialization, low adaptability, and low mobility, montane species are more affected by climate change than species that occur at medium and low altitudes. Here, we characterized the climatic space occupied by two montane species that differ in the range of spatial occurrence to compare the effects of climate change on their distribution over time. We characterized the climate niches of two arboreal mice, <i>Juliomys ossitenuis</i> and <i>Juliomys pictipes</i> (Rodentia: Cricetidae) using niche equivalency and niche similarity tests. We also investigated the potential effects of climate oscillations on the environmental suitability of both species from the Last Glacial Maximum 21,000 years ago to the year 2070 under different global warming scenarios using climatic modeling. Our research shows that <i>J. pictipes</i> and <i>J. ossitenuis</i> share a climatic niche, but have different occupancy densities and climatic ranges, suggesting that they may respond in different ways to climate change in addition to spatial niche segregation. <i>Juliomys pictipes</i> lost less suitable area with increased temperature and reduced precipitation than <i>J. ossitenuis</i>, which showed more significant events of reduced suitable area and altitudinal movement. We conclude that <i>J. ossitenuis</i> and <i>J. pictipes</i> segregate climatically and that <i>J. ossitenuis</i>, a species restricted to higher altitudes, is more susceptible to climate change.</p>