This report analyses and interrogates the accountability and transparency regime of the European Union’s border agency Frontex. Frontex was established as a European Union agency in the field of border, migration and asylum policies in 2004 and began operating in 2005. Over the last 15 years, the mandate of the agency, originally tasked with coordinating the operational management of the European Union’s external border through support to the EU’s member states, has expanded significantly. Through a series of reforms, most notably in 2007, and 2016 and 2019, the agency has become a pivotal actor in what is referred to as ‘European Integrated Border Management’. Since the creation of the agency and its first operations, there has been significant concern, both from the European Parliament as well as NGOs and other civil society organisations that the executive mandate of the agency has not been counterbalanced by effective mechanisms for accountability, particularly with respect to fundamental rights. To an extent, the Frontex monitoring and accountability regime has improved since 2011 through legislative change, thus strengthening the above mechanisms. The findings of the report however show that despite the continued expansion and strengthening of monitoring and accountability mechanisms since 2016, these efforts have again not resulted in an effective system for monitoring, investigating, addressing, and preventing fundamental rights violations at Europe’s external borders.