This book critically examines the effectiveness of EU humanitarian aid delivery in the wake of multiple crises.Focusing on four primary case studies - Myanmar, Lebanon, Mozambique, and Mali - which present distinct crisis types (complex, human-made, and natural), it reveals why the effectiveness of EU humanitarian aid programmes varies in relation to pre-established objectives. Drawing on extensive interviews and official documents from UN, EU, and NGO officials, the book introduces an innovative, multidimensional theoretical framework conceptualising effectiveness beyond goal attainment, encompassing needs assessment, the seamlessness of the policy cycle, and the transition between humanitarian and development aid. The book argues that EU humanitarian aid effectiveness is primarily influenced by institutional, relational, and political factors rather than by the type of crisis or funding gap. In particular, the attitudes of national authorities toward donors and implementing agents are the most decisive factors, followed by the quality of coordination among donors and agents. The book ultimately suggests that adopting a holistic, 'resilience-first' approach that integrates humanitarian and long-term development goals, creating integrated funding instruments that enable comprehensive responses from the outset, and fostering collegiality and formal and informal relationships among staff can lead to greater overall effectiveness.This book is of key interest to scholars, students, and practitioners in EU foreign policy, humanitarian aid, development studies, and more broadly to International Relations and policymakers.