Multiple citizenship is not possible
On 1st January 2000, new nationality legislation came into force, whereby migrants who have already been nationalised as Germans can lose their German nationality if they take on that of another country. There are a few exceptions, but these are very rare. It means, for example, that people who were born in Turkey and have become German nationals cannot at the same time retain Turkish nationality.
Loss of German nationality
The consequence of this fact is that the people affected once again have the status of foreign nationals and need a residency permit in order to continue living in Germany. As many people are still unclear about this, the Federal Ministry of the Interior has published a comprehensive brochure specifically for people with Turkish roots.
Information and explanation
The facts of the situation are explained in Turkish. The consequences are listed in the brochure step by step, along with details of contact centres, where people affected can gain help if it's already too late.