Political corruption is rampant in—and destructive to—many parts of the world. A growing number of international organizations (IOs) claim to address the problem by encouraging good governance norms and rules, such as anti-corruption standards and practices. Whether membership in IOs dampens corruption, however, is unclear. Our central argument is that the characteristics of IO membership determine both whether corruption is tolerated and the extent to which formal anti-corruption rules effectively combat the problem. First, groups of corrupt states are reticent to enforce good governance norms or rules against other IO members, rendering punishment for corruption incredible. Second, leaders may witness the value of corruption to their IO peers and learn to act the same way. Using a variety of data sources and estimation strategies, including new data on IO anti-corruption mandates, we demonstrate that: (1) countries that participate in member-corrupted IOs are significantly more likely to engage in corruption themselves—and experience an increase in corruption over time—than are countries that participate in less corrupt IOs; and (2) this tolerance for corruption occurs even within IOs that have adopted formal anti-corruption mandates, rendering good governance rules largely cheap talk among organizations governed by corrupt principles.