The authors contribute with the chapter “An ever weaker Union? The European Union in Global Governance Institutions”, where they question why a stronger single voice does not necessarily turn the EU into a more effective actor in global institutions. They argue that under certain conditions a stronger EU “single voice” does not lead to more ability to exert influence. They identify three processes that may explain the phenomenon: the EU’s efforts to establish a “single voice” may by themselves diminish its efficiency and flexibility in global institutions; the EU “single voice” is perceived by other actors as neo-colonial voice; and negative changes in the international structure shrink EU’s “single voice” influence. The authors use three case studies in their analysis: the roles of the EU in the UN Human Rights Council, the Kimberley Process to ban the trade of conflict diamonds, and the processes to ban cluster munitions.