This chapter considers the role of non-governmental organizations (NGOs) in the peace-security-development nexus. It begins by considering the history of the nexus focusing on important paradigm shifts to human security and rights-based approaches to peace, development and security. The chapter examines the implications of human security and rights-based approaches (RBAs) for NGO policies and practices and particularly how the political requirements of RBAs affect NGO service delivery and accountability. Then the chapter also discusses how the institutional and political challenges NGOs face generate constraints and limitations on their ability to implement nexus policies. The nexus is also a practical reality where lines between peace, security, and development are increasingly blurred. Embracing politics and advocating for reform has implications for NGOs’ ability to work within the nexus.