Non-governmental organizations (NGOs) are widely regarded as a force for good in international politics, representing sections of global society that would otherwise be without effective advocates. In order to accomplish this mission, NGOs are now widely accredited to and incorporated into the accountability mechanisms of global governance organizations (GGOs). Yet NGOs themselves need to show that they are accountable to the public. This chapter examines both sides of the same coin, and thus elucidates the reflexive relationship between NGOs and accountability. While various systems are now in place in order to strengthen the accountability of NGOs, recent changes in the organization of global governance present new challenges for effective accountability both of GGOs and NGOs. Taking the example of the Internet Corporation for Assigned Names and Numbers (ICANN), the chapter illustrates how the emergence of new transnational GGOs can challenge now established notions of NGO accountability and the role of NGOs as accountability guardians in global governance.