As international organisations and partnerships tackle increasingly complex global challenges, the need to incorporate diverse perspectives into decision making has grown and civil society engagement at the international level has expanded, becoming a common practice for reaching those directly impacted by global policies. Drawing on a comparative analysis of existing engagement models and interviews with officials and civil society organisations (CSOs), this OECD Working Paper explores opportunities and challenges for stakeholder participation at international level, formulating recommendations to help international decision makers and CSOs design structured, inclusive, and effective participation mechanisms for civil society and citizens.