Commercial security is increasingly present in humanitarian and post-conflict settings. The UN has even considered using commercial security to solve peacekeeping shortfalls. Yet using commercial security in these settings raises difficult ethical, operational and strategic questions. This exploratory study begins to describe the decentralized, ad hoc use of commercial security in these settings, in an attempt to provoke the further research and discussion needed before these questions can be adequately answered. The study involved forty-four interviews with senior officials, describing their organizations’ relations with commercial security providers. It deals with a wide variety of users and providers, while highlighting common themes and previously obscured fault lines.