The expectation that international organizations (IOs) can play a role in the resolution of violent conflict has spawned a process of institutional growth in the post-Second World War period. IOs at all levels have expanded existing instruments of conflict management and have gradually established new ones, such as mediation support units, early warning systems and standby military forces. Empirical research on this process has suffered from a lack of systematic, cross-temporal data. Seeking to rectify this weakness, this article introduces an original dataset on the institutional design of 21 peace-brokering IOs, organizations endowed with standing capabilities for conflict management interventions. The dataset contains yearly observations on 14 institutional variables during the 1945–2010 period, centered around three instruments of IO conflict management: mediation, economic sanctions and peacekeeping. It also includes observations on IO membership characteristics, power polarity and a set of security-...