Conifer forests dominated by Araucaria pines (Araucaria angustifolia) are emblematic of the humid forests in the southeast of Brazil, South America. However, these forests are highly fragmented and threatened by climate change. Despite the ecological and cultural importance of the dominant species (A. angustifolia), our knowledge of its climatic niche is incomplete. We aimed to understand the environmental drivers of the distribution and the climatic vulnerability of A. angustifolia in Brazil by modelling the extent of suitable climatic niches available for the species under the current climate and future climate scenarios. The potential distribution predicted by our model for the present was consistent with the real distribution of this species. However, our projections for future distributions show a decline in suitable climatic niches for the species, and a tendency for the species to be confined to high altitude mountain ranges and plateaus of south and southeast Brazil. Critically, most of the current protected areas will cease to harbor suitable climatic niches for the species. We conclude that prioritizing and expanding protected areas in important mountain ranges will be essential for protecting of the species in situ and to safeguard it from further habitat loss. Further research on population-level physiological responses of the species to climatic change and the role of biotic interactions will help optimize future modelling work.