This paper looks at rights in practice to understand how migrant EU citizens’ formal social rights translate into substantive ones. It highlights a factor thus far overlooked in the literature on welfare states and migrants’ social rights: namely, the actors involved in welfare delivery. The argument is based, first, on non-profit organisations’ (NPOs) function as ‘rights intermediaries’; and second, on the distinct make-up of the ‘welfare mix’ across countries, with which NPO’s role in the provision of services, and hence their capacities and autonomy, varies. Focusing on EU citizens’ cross-border social rights, and drawing on in-depth research in Germany and Sweden, the paper reveals how NPOs defend and facilitate access to rights in both countries. Yet NPOs’ extensive role in the German welfare sector generates greater capacities for NPOs to pursue inclusive objectives than what is available to their Swedish counterparts, which occupy a much more limited position as welfare providers. This, it is argued, can be important for understanding how boundaries of social citizenship are drawn in each country.