Résumé : The dissertation is about the impact of the European Union (EU) on the foreign policy of a candidate in the pre-accession period. More specifically, the research analyses the factors and processes that intervene between the EU power to generate change in Turkish foreign policy and Turkish national compliance with the EU conditions between 1997 and 2005 by way of analysing three cases: Turkish foreign policy towards Cyprus issue, Greek-Turkish bilateral problems in the Aegean Sea; and Turkey’s stance vis-à-vis the launch of the ESDP. Main question the research addresses is “why does a candidate choose to comply (or fail to comply) with the EU conditions in foreign policy?” In other words: “How (through what mechanisms) does the EU generate compliance with the EU conditions in foreign policy?” The dissertation approaches these questions through the perspective of the Europeanization literature and its conditionality school drawing on the Rational Choice Institutionalism. In accordance with this rationalist account, main argument the doctoral research intends to prove is that “the EU’s adaptational pressure on Turkey (operationalized as a function of clear/attainable membership perspective and credible conditionality policy) is a necessary yet not a sufficient condition for domestic compliance in foreign policy if the cost of compliance is high for the target government. In this respect, domestic actors’ strategic calculation is the ultimate determinant of the compliance degrees at the domestic level. In order to prove this core hypothesis, the research used theory testing process-tracing, longitudinal comparison of cases, counter-factual reasoning and the use of a control case. The evidence for testing the argument comes from the measurement of conditionality (measured as the linkage between a given foreign policy condition and membership-related reward) and domestic compliance (measured as foreign policy output ranging from rhetorical to behavioural change) through the content analysis of primary documents. This analysis is complemented with 33 semi-structured elite interviews. The dissertation by proving that the EU’s transformative power in foreign policy works through the cost and benefit calculation of the ruling party and by elaborating on the conditions under which the EU can interfere with this rational calculus (hence modify the opportunity structure for the target government), advances our understanding of the EU’s transformative power and contributes to the Accession Europeanization literature in general. Furthermore, the study provides additional empirical as well as theoretical in-depth case knowledge to the available literature on the Europeanization of Turkey and Turkish foreign policy.