In Turkey, the concept of migrant integration has risen to prominence in both academic and policy fields following the arrival of Syrian refugees. In this article, we first trace the resurgence of migrant integration studies in Western Europe in the past two decades following the decline of the discourse on multiculturalism. We argue that the policy concept of migrant integration has travelled to Turkey as part of the European Union’s (EU) externalization of migration management; however, the term has been reshaped in Turkey through a process of vernacularization as displayed in official documents, programs, and projects funded by the EU and other supranational actors, and policy studies. Although the vernacularized form of integration, named ‘harmonization’, has gained specific connotations in the Turkish context, this article demonstrates that it still carries assimilationist features, since it cannot go beyond the limits of the nation-state as the fundamental unit of analysis, and cannot escape from the binary opposition of native citizens and migrants. The article elucidates how knowledge production by governmental institutions, supranational and international organizations, researchers, and the civil society helps legitimate a certain understanding of integration of migrants into the host society that assumes each group to be homogeneous in terms of socio-economic characteristics and culture, and which emphasizes Islam as a common denominator between the two.