This chapter considers the extent to which Turkey’s customs union with the European Union (EU) can be considered a lasting form of ‘privileged partnership’ without envisaging further integration between the parties. It argues that the customs union was never intended as a goal in itself and that in its current form it does not constitute a sustainable form of privileged partnership. First, the chapter relates the current institutional shortcomings of the customs union to their historical roots. Second, it looks into the changing nature of the EU’s new generation trade agreements and the challenges they present for Turkey’s customs union such as their unparalleled impact on Turkey’s foreign trade. Third, the chapter discusses how the customs union may be modernized to bring EU-Turkey economic relations up-to-date with the EU’s new trade agenda. Lastly, it takes into consideration the political challenges that stand in the way of modernizing the customs union from both Turkish and EU perspectives.