The intensification of climate change combined with demographic shifts poses significant challenges for sustainable economic development in the European Union (EU). This study examines Romania’s position relative to other EU member states in the green transition, integrating economic, environmental, and demographic indicators into a comparative analytical framework. The research investigates the interrelationships among these indicators, with demographic dynamics conceptualized through the lens of the labor force. The analysis is based on data collected from Eurostat and Our World in Data, covering a sample of EU member states representing different levels of economic development. To identify similarities and differences across countries, scatter-plot analysis and agglomerative hierarchical clustering (AHC) were applied using five key indicators: gross domestic product per capita (purchasing power standard), CO₂ emissions per capita, primary energy consumption, the share of renewable energy, and the proportion of the active population to the total population. Based on these data, two research hypotheses were formulated on the relationship between economic development and sustainability performance. The results highlight the formation of clusters, generally comprising: (i) highly developed countries with high emissions; (ii) developed countries with effective green transition policies; and (iii) less developed economies, including Romania, characterized by relatively low emissions and increasing shares of renewable energy consumption. However, there are exceptions, such as Sweden and Denmark, which, despite being developed countries, cluster with Romania due to their high renewable energy consumption and low CO₂ emissions. Although Romania is gradually aligning with European sustainability policies, its transition remains constrained by structural limitations, energy dependency, and demographic and economic challenges.