How can international organizations (IOs) like the United Nations (UN) and their implementing partners be held accountable if their actions and policies violate fundamental human rights? This book provides a new conceptual framework to study pluralist accountability, whereby third parties hold IOs and their implementing partners accountable for human rights violations. Based on a rich study of UN-mandated operations in Afghanistan, Bosnia and Kosovo, the EU Troika's austerity policy, and Global Public-Private Health Partnerships in India, this book analyzes how competition and human rights vulnerability shape the evolution of pluralist accountability in response to diverse human rights violations, such as human trafficking, the violation of the rights of detainees, economic rights, and the right to consent in clinical trials. While highlighting the importance of alternative accountability mechanisms for legitimacy of IOs, this book also argues that pluralist accountability should not be regarded as a panacea for IOs' legitimacy problems, as it is often less legalized and might cause multiple accountability disorder.