The European Union (EU) has been a decisive actor in Turkey’s long journey of democratization, and this is due to substantial impact of the EU democratic conditionality on Turkish reform process. However, whether this effect will be persistent or not, is depended on the existence of a credible EU approach towards Turkey. Slow down in Turkey’s democratic consolidation in the post- 2004 period due to increasingly sided and discriminatory approaches of the EU as regards to Turkey’s accession process is an indicator of this fact. In this respect, analyzing three different period (pre- 1999, 1999-2004 and post- 2004) of EU-Turkey relations, the thesis investigates how the variance in the credibility of the EU conditionality affects the variance in the speed and quality of democratic consolidation in Turkey.