Although the European Union contains many developed countries, it is a union which experiences various problems originating from regional differences. After each enlargement process, less developed countries which have significant regional disparities joined the Union. In parallel with these enlargements, regional inequalities became a greater issue, and it was required to address regional policies once again. The European Union attaches great importance on reducing regional inequalities. In order to reduce these inequalities, various funds are provided and numerous projects are carried out. However, regional inequalities continue and in some instances, it is observed that regional disparities even increase despite the attempts aimed at regional development. Following the officially recognition as a candidate for full membership, Turkey brought various regulations into effect in line with European regional policies and addressed regional problems more intensely. Even though Turkey started to put emphasis on regional policies, regional disparities become more apparent in the last years. Within the scope of this framework, how regional disparities change in the European Union member states will be investigated first. In the light of these examples, this study aims to anticipate the impacts of Turkey’s accession process and possible membership to the Union. The analysis results show that not all countries benefit from the European Union considerably. Even in instances that are observed positive impacts in general economic situation, regional differences might increase. It is considered that Turkey will experience both positive and negative effects in this accession process.