After the JDP came to power in Turkey in 2002, much has changed in Turkish foreign policy as well as profound changes in international, regional and domestic contexts surrounding it. Particularly fluctuations in Turkish-Iranian relations in the course of seventeen years have been very puzzling, and complicated, which made it worthy of study. Once, relations between the two states have so improved that some pundits regarded it as an evidence of shift of axis in Turkish foreign policy. Soon later, Ankara and Tehran embroiled in a regional competition that reminded the Ottoman-Safavid rivalry of the 16th century with its strategic and sectarian implications. Later on, they have developed amicable relations. Against this background one may question how could we understand that very dynamic nature of Turkish-Iranian relations? Considering this complicated and dynamic picture, we should analyse decisive factors in the relations between Ankara and Tehran. In other words, what has changed - and has been changing - in Turkish-Iranian relations after the JDP? In order to comprehend the complicated and dynamic interactions between Ankara and Tehran, this research goes beyond the JDP period in Turkey and put forwards a review of the history of Turkish-Iranian relations. And then, it focuses on the JDP period and analyse relations between Ankara and Tehran from diplomatic, economic and regional perspectives. Finally, it makes some speculations on the future of Turkish-Iranian relations. It argues that the complicated relationship between the two countries have been determined by a configuration of geopolitical context, structural factors, and the ruling elite. The JDP elite have employed rationalization, institutionalization and compartmentalization strategies to further Turkish-Iranian relations. However, they could not go beyond the diplomatic culture that set the longer history of interactions between the two countries on a fine course between bitter rivalry and friendly relations.