Mass media are commonly held responsible for strengthening bonds of national solidarity and supporting relationships of mutual support among citizens as members of a political community. At the same time, mass media increasingly raise questions of global justice and through their coverage of distant suffering confront audiences with their moral responsibility to provide assistance to strangers. The notion of solidarity as grounded in global justice is therefore not only an abstract normative and legalistic principle but, sociologically speaking, is also linked to an expansive logic of building solidarity relationships of modern society as a community of strangers. To investigate this relationship between the media and (trans)national solidarity, the chapter discusses the role played by old and new (digital and social) media in establishing solidarity relationships among individuals across established borders of political community. It gives examples of mediated solidarity discourses in which mutual obligations between states and equal rights of citizens across borders are discussed controversially. It is argued that the Janus-faced nature of the media as a transmission mechanism for universal notions of justice (representing the world) and as the filter for the consolidation of thickened and contextualised relationships of solidarity within a community of equals (representing the nation) offers an opportunity for transnational solidarity mobilisation.