Chapter 4 revisits functionalism to study IO depoliticization. It argues that IO depoliticization practices follow functional and pragmatic logics of action. Based on various cases from the 19th to the 21st centuries in the fields of telecommunication, labor, development, environment and peacekeeping, it first demonstrates that IOs, and especially their bureaucracies, define their action as a concrete answer to people’s needs and states’ demands. The chapter then shows that IO depoliticization practices fall under a form of practical rationality: staff and members can favor depoliticization when it is perceived as a pragmatic and accommodating way to bypass controversies and facilitate cooperation. In return, however, IO depoliticization increases fragmentation within the system and contributes to stigmatizing politics.