In this study, it is emphasized that Turkish citizenship is important in two aspects. First, in the context of Turkey's diaspora policy, Turkish citizens living abroad as the subject of Turkish diaspora (citizens, fellow descendants, relative communities, etc.) have many rights with the effect of Turkish citizenship status in Turkey. This is a natural result of the definition of Turk which is associated with Turkish citizenship in the Constitution of the Republic of Turkey (article 66). Secondly, Turkish citizenship, especially for Turks living in European Union (EU) member states, brings important legal rights in the context of EU law. At this point, the decisions of the European Court of Justice (ECJ), which are examined within the scope of the study, also reveal an important legal basis for these rights. The study is structured over three research methods. First, the policies were resolved on Turkey's diaspora policies. This analysis was done on three pillars: (i) review of the literature on diaspora and Turkish diaspora, (ii) the examination of Turkish law, (iii) analysis of the applications and implementations of the relevant institutions of Turkey. Second, the study focused on the legal background of the rights of Turkish citizens set forth by Turkey-EU association law. Thirdly, and lastly, the recent ECJ decisions have been examined due to their interpretation of the current developments and controversial situations arising in the relations of Turkish citizens with EU member states and their binding provisions. As a result of the research, Turkish citizenship has been identified as a legal tool that brings important rights, gains and privileges for Turkish diaspora (Turkish citizens living abroad) in their relations both with the (EU) countries they reside in and their home country, Turkey. [ABSTRACT FROM AUTHOR]