This article examines the conditions that foster state-insurgent cooperation in rebel governance. State-insurgent cooperation is puzzling because it can alienate hardliners, undermine the parties’ legitimacy, reveal sensitive information, and cause autonomy losses. We propose that conflict parties are more likely to discount these costs when they have overlapping civilian constituencies with high governance provision expectations. Analysing rebel governance in Côte d’Ivoire and Sri Lanka using original data, we find that civilian expectations prompt cooperation even when the parties appeal to separate constituencies. The article nuances existing theories of rebel governance and contributes new knowledge on state-insurgent interactions in civil war.