The EU Ecolabel, established in 1992, aims to promote sustainable consumption, yet a significant gap persists between consumers’ positive environmental attitudes and their actual purchasing behavior of ecolabeled products. This study examines the attitude–behavior gap in EU Ecolabel adoption across Europe, leveraging data from the 2023 Eurobarometer survey with 26,630 valid responses from all EU member states. Using mediation path analysis, the research investigates the factors mediating the relationship between environmental knowledge and purchasing behavior, including environmental attitude, ecolabel trust, and environmental concern. The study applies an integrated theoretical framework combining the Knowledge–Attitude–Behavior model and Attitude–Behavior–Context theory to explain the complexities of consumer behavior towards ecolabeled products. The findings reveal the interplay of direct and indirect effects among ecolabel knowledge, trust, environmental concern, attitude, and buying behavior, while also considering demographic factors’ influence such as age, gender, education level, and residential setting. The research provides a comprehensive cross-country analysis within the EU, offering insights into bridging the attitude–behavior gap and enhancing the adoption of eco-friendly products. The results have significant implications for policymakers, marketers, and researchers in promoting sustainable consumer behavior, improving environmental label effectiveness, and developing targeted interventions to increase ecolabel adoption rates.