Nonnative feral ungulates have both direct and indirect impacts on native ecosystems. Hawai`i is particularly susceptible to biological invasions, as the islands have evolved in extreme geographic isolation. In this paper we explore the ecological impacts of nonnative feral goats (Capra hircus) in the Hawaiian Islands, including both the current state of knowledge and future research directions to address knowledge gaps. Understanding how invasive vertebrates impact island ecosystems is important as it provides an informed context for developing contemporary solutions to pressing management problems. Current knowledge gaps, such as the behavioral ecology of goats and their impacts on specific plant species and communities, limit the effectiveness of ecological restoration and conservation in Hawai`i. Emerging technologies in wildlife tracking and remote sensing will enable a greatly improved understanding of the behavior and ecological impacts of these nonnative animals in what is already a highly degraded ecosystem.