This article argues that migration has evolved into a conflictual parameter in the institutionalization of the EU-Turkey relationship and that it plays a significant role in the formation of instability as the main feature of this institutionalization process. Moreover, migration in its nature is a dynamic/non-linear social phenomenon which makes an institutionalization process highly open to exogenous effects and quite unstable. Therefore, contrary to the mainstream institutionalist approaches, this case study argues that an institutionalization process does not necessarily bring about continuity in the wake of an exogenous shock, but if an institutionalization process contains conflictual parameters (like the migration issue) with a strong connection with endogenous and exogenous dynamics, instability/change might become the main feature of it. From this point of view, this study anticipates that the migration-like dynamic parameters will keep the European integration as an ongoing process in the future, and its structure will be subject to a continual change. Furthermore, this change-oriented institutionalization might make the EU more heterogeneous and multi-dimensional in time. Related to this anticipation, even though the migration issue plays an inhibitor role in Turkey's accession process to the EU at the moment, it might play a catalyst role in this process by making a differentiated membership a more reasonable option for both the EU countries and Turkey in a more differentiated EU structure in the future.