The Fitzgerald River National Park is one of the world’s 25 biological hotspots, containing many endemic flora and fauna species. Its unique biodiversity is being threatened by the introduced root pathogen, Phytophthora cinnamomi. We evaluate the cost-effectiveness of strategies to manage Phytophthora cinnamomi in the park, using the Investment Framework for Environmental Resources (INFFER). Management strategies based on current and higher investment levels are shown to have high Benefit Cost Indices. These results support the use of public conservation funds to address the threat of Phytophthora cinnamomi, and show the need for improved understanding of the impact and the adoption of strategies.