In this article we argue that the Member States of the European Union (EU) have consistently, since its inception, developed a shared framework to measure, monitor and intervene to improve the health status of its population, while invoking the subsidiarity principle for the health sector. As a result, a European Health Union (EHU) has been emerging insidiously and consistently, following the concept of a system for health. Using the World Health Organisation Building Blocks Framework, we analyse the normative and institutional developments related to EU citizens' health that have created a de facto EHU. Developments towards an EHU remain unequally distributed among the different building blocks analysed. The existing EHU is the result of a fragmented and incremental process, mostly grounded in governance, health intelligence and services' development. Health crisis, the Commission's agenda‐setting activities and market pressures have been the most important push factors for these step‐by‐step processes.