Case studies suggest that ethnic groups with autonomous institutional arrangements are more prone to secede, but other evidence indicates that autonomy reduces the likelihood of secession. To address this debate, we disaggregate their autonomy status into three categories—currently autonomous, never autonomous, and lost autonomy—and then unpack how each shapes the logic of collective action. We argue groups that were never autonomous are unlikely to mobilize due to a lack of collective action capacity, whereas currently autonomous groups may have the capacity but often lack the motivation. Most important, groups that have lost autonomy often possess both strong incentives and the capacity to pursue secession, which facilitates collective action. Moreover, autonomy retraction weakens the government’s ability to make future credible commitments to redress grievances. We test these conjectures with data on the autonomous status and separatist behavior of 324 groups in more than 100 countries from 1960 to 2000. Our analysis shows clear empirical results regarding the relationship between autonomy status and separatism. Most notably, we find that formerly autonomous groups are the most likely to secede, and that both currently autonomous and never autonomous groups are much less likely.