Socio-economic sustainability (SES), defined as the ability to achieve economic growth without harming the long-term interests of the society and to meet the needs without harming the environment, is a critical agenda item for many countries. Analysing the SES levels for the European Union (EU) countries, which are faced with many social, economic, cultural, and political changes in the globalization process, is a strategic research topic. The aim of the current study is to develop an approach that can compare the SES performances of the EU member and candidate countries with a multi-criteria approach. For this purpose, a methodology based on Entropy and MAIRCA techniques has been proposed. In practice, thirty-two EU member and candidate countries were evaluated by considering ten criteria. As a result of the study, it was seen that the criteria with the highest weights were the income share of the poorest 40 percent (0.237), concentration index (0.168) and R&D expenditures (0.146). While the most successful countries in terms of SES performance are Denmark, Austria and Sweden, the most unsuccessful countries are Southern Cyprus, Greece, and Ukraine. The proposed approach will allow evaluation of both the importance of SES criteria and the status of alternatives.