The processes of Europeanisation—meaning the deepening of European integration on various levels—have previously been discussed from the point of view of political science, economics, linguistics, and cultural studies, with a macro-perspective on states, institutions, and organisations. However, Europe and the European Union (EU) are populated by individuals, who are actors of European transnationalism, which this paper conceptualises as horizontal Europeanisation. Spatial mobility is also becoming more relevant for thriving academics, and the EU aims to close ranks in Europe in the field of higher education and research. Therefore, this paper asks how the process of horizontal Europeanisation among early-career academics manifests itself. This process is discussed against the background of the framework of the EU and the European Research Area (ERA), where academics make use of a common scientific market. The basis for the qualitative empirical analysis is 60 biographical interviews with intra-EU mobile doctoral candidates. The findings show that the EU and ERA contribute to the processes of horizontal Europeanisation and support it. However, many decisive factors for horizontal Europeanisation lie beyond the EU and the concept of ERA. The novelty of this article as a contribution to European studies is the explanation of horizontal Europeanisation among academics through spatial mobility patterns.