Öz
After a painful application process, Britain, was admitted to the European Union (EU) together with Ireland and Denmark in 1973. It has always been a problem in terms of internal policy independence and transfer of some sovereign rights for the EU. Britain has succeeded in decoupling from many supranational and intergovernmental agreements put into effect by the EU. Brexit is the most permanent of this divergence. In the Brexit process, it is seen that immigration is used as a propaganda tool. Considering the statistics, it is understood that the problem regarding immigration for the Britain is due to immigrant mobility with other member countries of the Union rather than being outside the region. This study investigates the economic and security-based effects of migration in the EU and in the Britain, while also discussing the relationship between the Brexit process and the issue of migration. It is understood that both the EU countries and the Britain consider the social change that occurs with immigration as a security threat. Developed and target countries have to take all kinds of political measures to protect themselves against this threat and prevent migration, and moreover, they feel they have this right.