Summary Of all the introduced mammalian pests, rodents are the most common invaders of islands and have triggered numerous extinctions around the globe. They have a short gestation period and large litter size, giving them the ability to colonise new areas rapidly. The same biological traits make them difficult to eradicate. Although the biodiversity benefits of removing exotic rodents from islands are increasingly being recognised, there are few published analyses of eradication attempts that critically evaluate eradication tools. This study examined the response of House Mouse (Mus musculus) populations to an eradication operation on Montague Island, Australia. While the specific impacts of mice have not been studied on this particular island, elsewhere they have been shown to have negative impacts on a range of species including plants, invertebrates, lizards and seabirds. On Montague Island, mouse abundance across different habitats was examined using mark–recapture data collected before and after the deployment of brodifacoum baits. Data obtained before baiting showed significantly lower numbers of mice in sites dominated by exotic grass compared with those dominated by native vegetation. Mouse numbers overall were declining during winter and the population was not breeding, making this an optimal time to undertake the eradication. Trapping immediately after the initial bait drop failed to capture any survivors, and no individuals have been detected during the 3 years since the deployment of baits. This study demonstrated that both small and large baits (0.6 and 2 g pellets) were effective in eradicating the House Mouse from Montague Island. While present, mice were probably slowing the re-establishment of native vegetation by grazing seedlings and consuming seeds. With this pest now gone, the process of natural regeneration is expected to accelerate. The eradication of the House Mouse from Montague is likely to have other positive effects on the island’s biodiversity. The operation itself contributed to enhancing local capacity to eradicate exotic rodents from larger or more complex islands.