This study investigates the key factors influencing sustainable consumption behaviour among young adults aged 18 to 35 in Georgia and Portugal. Using a mixed-methods approach combining survey data from 261 participants and insights from 14 semi-structured interviews, the research explores the role of education, cultural values, governmental support, and trust in green marketing in shaping consumer decisions. The findings reveal that while youth in both countries express interest in sustainability, Portuguese participants are more likely to trust green marketing, actively seek information on sustainability, and perceive government initiatives positively. In contrast, Georgian respondents are more influenced by personal health benefits but face greater challenges, such as economic constraints and limited access to eco-friendly products. Education emerged as a key enabler of sustainable behaviour, though a gap remains between knowledge and action. These insights contribute to understanding sustainable behaviour across diverse cultural contexts and offer practical recommendations for policymakers and businesses aiming to foster environmentally responsible consumption.