Abstract This report studies the developments in 28 EU Member States of three types of dual citizenship restrictions in the period 2010-2020, namely 1) requirements to renounce the original citizenship upon the acquisition of citizenship (Globalcit modes of acquisition A05-A27), 2) provisions stipulating the loss of citizenship upon the acquisition of a foreign citizenship (Globalcit mode of loss L05), and 3) provisions stipulating the loss of citizenship upon the retention of a foreign citizenship (Globalcit mode of loss L06). The report shows that, on 1 January 2020, a majority of 16 EU Member States had none of these dual citizenship restrictions in place, while 12 other EU Member States imposed at least one of these three restrictions. However, the report also demonstrates that these 12 restrictive states have significantly mitigated dual citizenship restrictions by offering – often wide-ranging – exemptions to their main rule. The report also shows that between 2010 and 2020, nine EU Member States have introduced amendments in domestic citizenship law that relate to dual citizenship. In seven of these countries, the changes amounted to an increased toleration of dual citizenship. Next to that, the report uses the concept of ‘citizenship constellations’ to study the interactions between dual citizenship provisions in EU Member States, concluding that a majority of 61% of citizenship constellations were permissive constellations, covering no less than 92.4% of all EU citizens who acquired the citizenship of another EU Member State in 2018. Lastly, the report proposes a number of research avenues that remain to be explored. Keywords: Citizenship, Dual Citizenship, European Union