<p>This study examines the impact of university sustainability programs on students’ eco-behaviours in Turkey, focusing on the roles of perceived institutional support, personal environmental efficacy, and the potential for greenwashing. A total of 485 students from various Turkish universities participated in a quantitative survey which were selected through purposive sampling method. The analysis, conducted using Partial Least Squares Structural Equation Modeling (PLS-SEM), confirmed several hypotheses. The findings indicate that engagement in sustainability programs positively influences students’ eco-behavioural intentions, mediated by both environmental attitudes and personal efficacy. Our findings further revealed the significant impact of perceived institutional support on students’ eco-behavioural intentions, as well as its significant moderating role in the relationship between sustainability program engagement and students’ environmental attitudes. Our study suggests that perceived greenwashing can undermine trust and engagement. The study underscores the importance of transparency, comprehensive sustainability education, and robust institutional support to foster genuine eco-friendly behaviours among students. These insights contribute to enhancing the effectiveness of sustainability initiatives in higher education.</p>