The aim of the project “EcoHarmony – style, mindset and ecological economy” was to increase environmental awareness among young people from four European countries: Poland, Greece, Romania, and North Macedonia, representing diverse social, cultural, and economic backgrounds. The project addressed the need to reduce disparities in the level of ecological knowledge among participants coming from countries with different experiences in environmental education, climate policies, and access to pro-environmental initiatives. The project was targeted at young people aged 19–28 who were at a similar life stage related to entering adulthood and making their first professional and consumer decisions. The participants shared an interest in ecology, environmental protection, and active civic engagement; however, they differed in their level of knowledge, experience, and development opportunities resulting from their local contexts. One of the key objectives of the project was to enable mutual learning through the exchange of perspectives and experiences shaped by the realities of their countries of origin. The project aimed to activate young people in response to challenges related to excessive consumption and the phenomenon of fast fashion, which affects local communities in different ways across the partner countries. Through non-formal education and practical activities, the project sought to develop participants’ sense of environmental responsibility, critical thinking skills, and readiness to take action for sustainable development at both individual and local levels. An important objective of the project was also to create an international and inclusive space for cooperation that fostered the integration of young people, including those with fewer opportunities, and strengthened intercultural dialogue. The project enabled participants to build lasting international relationships, enhance their language and social competences, and jointly develop tangible results, such as a social campaign, which could be adapted and used in different national contexts after the mobility had ended.