Healthcare systems aim to provide access to good quality care, while ensuring equity and solidarity. The fiscal sustainability of healthcare systems has become a matter of concern in recent European Union (EU) debates, considering the ever increasing need for adequate healthcare determined by factors such as aging population, investments in technology and infrastructure, medical products and wages. Our paper seeks to measure the health system performances of the EU countries by building up a composite index, which will then be used as a tool in investigating the relationship between health performance and the fiscal sustainability of health systems. A principal components analysis (PCA) was applied to build the composite index through the use of the most relevant health indicators provided by Eurostat and the Sustainable Development Knowledge Platform. The composite index offers a comprehensive performance assessment and provides a clear ranking of the EU countries based on their health system performances. Further investigation of the link between health performance and fiscal sustainability revealed that higher ranks are associated with higher shares of health expenditures in gross domestic product (GDP), a large share of employment in the health sector, and higher duration of working life. These patterns are followed by efficient health systems, encountering reduced sustainability risks.