Conservation practitioners are increasingly embracing evidence-based and re- turn on investment (ROI) approaches. Much evidence now exists that docu- ments island biodiversity impacts by invasive mammals. The technical ability to eradicate invasive mammals from islands has increased exponentially; con- sequently, strategic planning focused on maximizing the ROI is now a limiting factor for island restoration. We use a regional ROI approach to prioritize erad- ications on islands for seabird conservation in British Columbia, Canada. We do so by integrating economic costs of interventions and applying a resource allocation approach. We estimate the optimal set of islands for eradication un- der two conservation objectives each with a series of increasing thresholds of population sizes and breeding locations. Our approach (1) identified the most cost-effective interventions, (2) determined whether or not those interven- tions were nested with increasing thresholds, and (3) helped justify larger in- vestments when appropriate. More often than not, conservation decisions are made at a regional scale, and decision-makers often must make choices on how to allocate funds across a number of potential conservation actions. A regional, ROI framework can serve as a decision-support tool for organizations engaging in discrete interventions in order to maximize benefits for the minimum cost.