This article analyzes the extent to which Turkey’s irregular migration governance has evolved since the 1990s and the most salient factors in that process. Relying on the methods of process tracing and political ethnography, the article demonstrates that, since the early 1990s, Turkey’s irregular migration governance has been driven by the following factors: 1) responses to the European Union’s (EU) attempts to control migration through externalization; 2) Turkey’s national security concerns, which increased with the advent of mass migration from the Middle East; and 3) the increase in the number of irregular migrants on Turkish territory. The Syrian mass migration that began in 2011 gave momentum to the evolution of irregular migration governance in line with the long-term externalization on the part of the EU. Our analysis sheds light on the interconnectedness of irregular and mass migration, as well as on the outcomes of interactions between international politics and national migration governance. Thus, the article provides insights that will prove valuable for migration studies, EU studies, and studies on Turkish foreign policy.