In this introduction, we argue for the need to better understand so- cial work with migrants and to enhance its research bases against a background of increasing mobility and ethnic diversification across Europe. While much has been written on the influence of international migration on national welfare regimes and on specific forms of social welfare provision, the ways in which mi- gration affects mainstream social work practices are relatively understudied—even less so in a comparative perspective, looking at social interventions as well as to the organizations and cultures of social services, without neglecting the broader policy arrangements in which social work practice is embedded. The political and pre- scriptive bases of social workers’ remit vis-a`-vis immigrant clients, the ways of framing and categorizing the latter, and the impli- cations for social workers’ training, supervision, and research are discussed. The main value added of the five contributions to this Special Issue of JIRS is highlighted at last.