Eradication is often the preferred method of invasive species management on islands; however, its consequences may affect native communities. Feral goats (Capra hircus), donkeys (Equus asinus), and pigs (Sus scrofa) were eradicated from Santiago Island in the Galapagos Archipelago by 2005. Because feral goats were the dominant herbivores on Santiago Island until their eradication, we examined the consequences of goat eradication on the diet of territorial Galapagos Hawks (Buteo galapagoensis) through a comparative study of observations of prey deliveries to nests before (1999–2000) and after (2010–2011) eradication. We predicted that vegetation recovery after eradication would limit the hawks’ hunting success of terrestrial prey and they would therefore switch to predominantly arboreal prey. We did not observe the predicted switch from terrestrial to arboreal prey in the diet; on the contrary, after goat eradication, hawks delivered significantly fewer arboreal prey items. However, introduced black rats (Rattus rattus) represented a significantly greater proportion of the hawks’ diet after eradication, particularly in moderate to dense vegetation (arid and transition habitats), replacing other prey items. Overall, 73% of total prey biomass delivered after eradication consisted of introduced rats, compared to only 20% before eradication. This study documents the complex interaction of predators and introduced prey, even in relatively simple ecosystems.