Chapter 9 summarizes our theoretical expectations and empirical findings about IO exits. It outlines the implications of IO exit for international cooperation, future research, and policymaking. It also provides additional insight into IO exits that have occurred as regional conflicts have engulfed the world in recent years, exemplified by Russia’s invasion of Ukraine in 2022. The chapter analyzes how IO exits might affect international cooperation as multilateralism is being contested on several fronts. It also discusses that patterns of democratic decline and polarized domestic politics may lead the future of IO exits to be different than the past. Even while this contestation is happening, however, we show that IO exits (as well as threats and reentry) extend beyond current affairs; they have been a relatively steady occurrence over time. We conclude by arguing that despite – and sometimes because of – occasional exits, international cooperation continues through IOs and a robust set of other international institutions. We outline several exciting areas for future research that may be inspired by the findings from this book.