Can international organizations (IOs) gain independence from their member states, even if their decisions arise from member state bodies? While organizational independence is a precondition for the autonomy and agency of IOs, International Relations theory cannot yet grasp IO independence in the absence of institutional agents like secretariats. Drawing on collective actor theories with a strong micro-foundation from philosophy and sociology, this article demonstrates how organizational rules and procedures gradually shape organizational processes and produce collective effects that do not arise from the aggregation of member state activities. Member-dominated IOs can produce collective beliefs about relevant parts of the outside world that differ from the aggregated beliefs of member states. They can comprise institutionalized organizational goals and criteria that indicate collective intentions of organizational action and differ from the aggregate preferences of member states. They can comprise decision-making procedures that foster organizational decisions according to collective beliefs and intentions and reduce or abolish the relevance of bargaining and preference aggregation. Finally, they can act in ways that do not immediately rely on implementation action by the member states or by other lower-level actors. I conclude that analyzing the sources of independence of member-dominated IOs from their members sheds light on the nature and effects of IOs as group actors.