Purpose – The objectives of this research are two-fold. First, the objective is to examine the impact of specific managerial characteristics (i.e., managerial ability and managerial overconfidence) on bank value in the ASEAN banking industry. Second, the objective is to examine the mediating effect of Environmental, Social, and Governance (ESG) performance in the relationship between managerial attributes and bank value, to identify the behavioral transmission mechanisms influencing corporate valuation. Design/methodology/approach – A quantitative methodology was employed for this study to analyze a dataset of 108 listed banks operating in the ASEAN region from 2015 until 2024. Regression based mediation analysis using Hayes' PROCESS macro was used to analyze data to determine both the direct and indirect effects of managerial characteristics on bank value as represented by Tobin's Q. Findings – Findings indicate distinct pathways exist for different managerial traits. Managerial ability has a significant direct positive effect on bank value and this effect is attributed to improved operational efficiency rather than improved ESG performance. In contrast, managerial overconfidence had a significant negative effect on ESG performance. Importantly, ESG performance is a full mediator in the relationship between managerial overconfidence and bank value since overconfident managers exhibit lower ESG performance which ultimately leads to decreased bank value. Research limitations/implications – These findings extend Upper Echelon Theory and Stakeholder Theory by providing evidence on how cognitive biases (e.g., overconfidence), versus technical competences (e.g., managerial ability) can have differential impacts on sustainability and value creation in emerging markets. The study is limited to the banking sector in ASEAN; therefore, future studies could be extended to include cross-industry comparisons to improve generalizability. Originality/Value – This research provides new insights into the limited existing literature on the behavioral antecedents of ESG performance in developing countries. The research demonstrates that ESG performance is not simply an outcome of strategy but also a behaviorally mediated channel by which managerial psychology affects the market valuation of firms in the ASEAN banking context.