Since World War II nations have formed alliances for reasons of security and trade. Countries have seen international integration as an appropriate approach to resolving domestic and international political issues, improving their welfare by both transforming their infrastructures and increasing their foreign trade. While the majority of these relationships are straightforward d Turkey’s relationship with the European Union is more complex due to differences in religion and, at times, political ideology from other Union members. As a candidate country Turkey has made advances towards the full membership of the European Union with the customs union being the most significant. The impact of customs union membership is discussed and the effects of the customs union on Turkey’s trade and economy are examined from a perspective of different economic theories.