The establishment and development of social policy is generally described as a response to the modern project. Whereas the establishment and development of social policy has developed in divergent ways in different nation-states, overall it has developed within a national frame. In the literature the so called “golden age” of western welfare states is even described in terms of national closures. These closures have from the outset been challenged by mobile individuals. Immigration brings in outsiders – should they access national social security schemes? Emigration carries out insiders – should they access national social security schemes from abroad? These are classical who-questions in social policy research, here related to mobility. Ongoing globalization and increased international migration have nurtured this field of inquiry, sometimes named transnational social policy. This study takes a historical stance on the issue. Under analytical focus is how discourses of mobility and belonging in Swedish social policy have transformed over time. The overall question dealt with is how we can understand Swedish state social responsibility towards transnational populations. More specifically it asks how different understandings of mobility and belonging in Swedish social policy have shaped (i) the access to social security for foreigners in Sweden and (ii) the portability of social security to outside of Sweden for citizens and foreigners. The analysis relies on written documents (statutory investigations, state reports, etc.). The study contributes to connect social policy analysis with mobility studies and it brings new insights to our understanding of Swedish social policies.