SignificanceTheoretical models of population dynamics have shown the counterintuitive conclusion that harvest can increase the equilibrium size of a population. These models of increases in response to mortality have been considered for fisheries harvest and removal of non-native species and can be driven by density-dependent overcompensation. This is the first controlled experimental field demonstration showing that harvest-driven overcompensation produced a 30-fold, single-year increase in the abundance of the invasive European green crab (Carcinus maenas), one of the world’s most invasive predators. Using multiple lines of evidence, we provide both a robust demonstration of a fundamental prediction of population models in a field population and an important cautionary message for future eradication efforts for similar invasive species.