<p>Establishing clear, rationales for conservation actions is critical to optimizing the chances of rescuing threatened species worldwide. We propose a simple habitat suitability index, a trade-off between occupancy probability and extinction risk, to guide conservation actions for the blond capuchin monkey (<i>Sapajus flavius</i>), whose distribution spans the contrasting but adjacent Atlantic Forest and Caatinga phytogeographic domains of northeastern Brazil. Our objective was to create a map to spatially coordinated management options considering both domains under two divergent but plausible scenarios assuming contrasting conservation outcomes: (1) active conservation efforts, in which government agencies/communities agree to invest and participate in conservation actions; and (2) no intervention and no additional effort. Based on the habitat suitability index, sites were classified into three types: A (protected and suitable, <i>n</i> = 3); B (suitable but under high extinction risk, <i>n</i> = 9); and C (unsuitable and highly defaunated, <i>n</i> = 75). Our results show that under Scenario 1 it would be possible to fund an active taskforce to improve forest quality in habitat remnant types B and C while supporting monitoring and protection of type-A sites. However, little can be done under Scenario 2 without successful educational programs to raise awareness and change the perception of local stakeholders. This study introduces a spatial index to prioritise conservation actions at key sites, providing a practical approach to effective resource management in a changing environment. Our protocol may be useful in guiding conservation action in the face of resource constraints and rapid environmental and climatic change in increasingly threatened biodiversity hotspots.</p>