Introduced mammals are a major driver of extinction and ecosystem change, particularly on islands. Feral goats Capra hircus have been introduced to numerous islands worldwide and have had wholesale impacts on ecosystems. Techniques are now available, however, to eradicate goat populations from islands, providing a powerful conservation tool. Goats were removed from Pinta Island, Galápagos, Ecuador after a 30-year eradication campaign, the largest removal of an insular goat population using ground-based methods. Over 41,000 goats were removed during the initial hunting effort (1971–82). In the following decade the island was twice wrongly declared free of goats. During this period, the island was visited irregularly but no monitoring programme was implemented. A revised campaign over 1999–2003, which included improved hunting techniques and monitoring, removed the final goats from the island. The use of Judas goats was critical in locating the remaining goats and as a tool to confirm eradication. A systematic monitoring programme is critical for confirming eradication and preventing future reintroductions. An earlier monitoring programme would probably have resulted in earlier eradication and significant financial savings. Given limited resources, island conservation programmes elsewhere should strive to increase eradication efficiency and learn from past campaigns.