In the academic literature, mainstreaming is conceptualized as a shift in policy focus (from specific to generic), as well as in governance (from state-centric to poly-centric). Whereas mainstreaming has been applied in various areas, such as gender, disability and environment, a more recent application concerns migrant integration, which has so far been under-studied in academic circles. This article provides a critical analysis of mainstreaming as a supposed ‘trend’ in migrant integration policies. It provides a conceptual discussion of what mainstreaming might mean in the field of migrant integration in an effort to connect the concept of mainstreaming as used in other fields to the literature on migrant integration, and notably the emerging concept of interculturalism. Following this, it provides an empirical analysis of shifts in integration governance and policy in Denmark, France, Germany and the UK in an effort to explain whether mainstreaming, as conceptualized, is taking place. The article concludes that mainstreaming as a concept in the field of migrant integration can only partially explain policy developments. There is, indeed, a clear trend towards more poly-centric governance and towards generic policies. However, such policies rarely involve efforts to create a generic awareness of migration-related diversity, and are often overshadowed by broader national narratives on migrant integration, and pre-existing governance structures. However, the existence of an explicit pursuit of replacement strategies at the local level suggests that mainstreaming approaches may be a way of circumventing these national narratives and governance structures