This study employs social cognitive theory to examine the dynamics of ethical climate, environmental passion, and low-carbon behaviours among Malaysian public servants based on data from 407 employees across 37 departments. Although ethical climate did not have a direct impact on low-carbon behaviour, a significant association with environmental passion was observed. Additionally, environmental passion exhibited a noteworthy relationship with low-carbon behaviour, and emerged as a mediator between ethical climate and low-carbon behaviour, with green mindfulness moderating this relationship. These findings underscore the importance of nurturing environmental passion and green mindfulness to promote low-carbon behaviour among employees and aid organisations in addressing environmental challenges. By addressing these empirical gaps, this study contributes to the literature on low-carbon behaviour and offers both theoretical insights and practical implications for sustainability initiatives.