Following the 2015-peak of asylum-seeking migrants in Europe, asylumpolicies have become increasingly restrictive. As bordering has become a prioritized issue among many European national governments, including in the Nordic countries, practices of bordering have also become more decentralised, diffuse and dispersed. This special issue set focus on such bordering practices as these are manifest in the social service sector. It draws on research conducted in Norway and Sweden and consists, besides this introduction, of seven original articles.Of particular focus is how social work, in its regulations and practices, are involved in the bordering of both the nation and the welfare state. Connecting insights from border studies – and related critical research – with social work research, the articles present empirical analyses of the dynamics of bordering practices among varying practitioners and in varying organizations, including legislators, courts, municipalities, street-level social workers and civil society organizations. The special issue as a whole also raises questions about the ethical and political challenges that emerge at the nexus of bordering and social service provision. In this introductory article, we provide an overview of the field of border studies and discuss how it relates to social work research. This serves as a conceptual foundation which we hope will enable critical reflections on the relationships between social service