The literature on migration has largely covered concepts of diaspora, such as transnationalism, immigration and religious-ethnic minorities. These concepts that concern related factors of social transformation, mainly with reference to Islam in Europe, have been investigated with respect to religion. Major research questions include whether, and how, Muslim communities in Europe keep self-identity and how they adapt to the environment without abandoning group identity. This article examines Muslim diaspora with its different facets in Europe, and with religion as a dynamic factor in diasporic social transformation. The study presents a delineation of this diaspora and its conflation with the issue of immigration, transnationalism and identity, and the dynamics of religious transformation within the Muslim diasporic space. Reference will be made to the theoretical framework developed by Steven Vertovec on diaspora, transnationalism and migration in its relation to religion. The article follows two major theoretical premises: (i) whether national identity and citizenship policy, as defined and regulated by political bodies, are politically charged; and (ii) the question of multiculturalism and integration in Europe in terms of the encounter between Islamic values and putatively "secular" European values, in a time when multiculturalism has been shifted to an "assimilative" mode of integration.