This chapter details the relevance of effective multilateralism for the Iran file. It aims to analyze the European Union's (EU) policy towards the Iran nuclear file. Actorness has been a central term to the debates about European foreign policy that has, however, remained obscure to many scholars of international relations. Effective multilateralism was the 2003 security strategy that popularized the term 'effective multilateralism', making it one of the EU's strategic objectives: In a world of global threats, global markets and global media, the security and prosperity increasingly depend on an effective multilateral system. It objectives that the development of a stronger international society, well functioning international institutions and a rule-based international order. The EU sees the world organization as a main stakeholder for global security governance that can, for lack of its own resources, at least legitimize collective action.