Tropical forests provide a suite of benefits including biodiversity, cultural value, and a range of ecosystem services. Globally, there is increasing interest in incentivizing native forest protection as a multi-benefit natural infrastructure strategy to secure clean and ample water supplies. In addition to conversion to agriculture and other non-forest land uses, non-native species invasion represents a major threat to these systems, particularly on islands. Whereas several recent efforts have quantified the benefits of reforestation or avoided agricultural expansion in tropical forest areas, the hydrologic and associated economic benefits of avoided invasion have received less attention. To address this gap, we quantified the benefits of protecting native forest from conversion to non-native forest in East Maui, Hawai’i in terms of groundwater recharge, a highly valued hydrologic ecosystem service that water utilities increasingly seek to co-finance.