This study aims to investigate whether banks’ environmental, social and governance (ESG) activities impact their profitability and stability. The authors also explore whether banking industry competition and the country’s regulatory quality moderate the impact of banks’ ESG on their profitability and stability. The sample includes data from 46 banks in 11 Organization of Islamic Countries (OIC) from 2010 to 2020. The authors have used the generalized method of moments (GMM) as the primary estimation model, with robustness tests to validate research findings. The results show that neither ESG nor its components impact bank profitability. Instead, ESG and its social component decrease bank stability. The findings neither support the stakeholder theory nor the risk-management view, which proposes that ESG activities improve financial performance and reduce unnecessary risks. However, an increase in market power (reduced competition) frees resources for banks, such that they focus more on ESG activities, which improves profitability, albeit at reduced stability levels. This finding supports the competition-related differentiation hypothesis. Finally, a country’s regulatory quality change does not influence bank ESG to impact its profitability or stability. This finding does not support the institutions-ESG proposition. This study has several limitations. First, constrained by data availability, the authors could not examine Islamic banks in OIC countries. Examining the ESG outcomes in Islamic banks would be interesting based on Islamic ethics and corporate social responsibility perspectives. The data set could also be more recent so that the differential impact of COVID-19 on bank ESG and financial performance could be estimated. The coverage of OIC countries was limited in our sample; this could be improved in future research. Banks should evaluate the focus and scope of their ESG activities, communicate their long-term strategic benefits with stakeholders and align ESG with their strategy and business model to offer innovative ESG-based products. They should also recalibrate ESG in their risk management framework to catalyse stability and stakeholders’ trust. Policymakers should control the level of competition so banks can foster ESG without sacrificing financial performance. Also, banks should be given regulatory incentives so ESG becomes integral to bank growth, direction and stability. ESG should be part of banks’ strategy and business model, to maximize its benefits for stakeholders, while maintaining competition and providing regulatory incentives. To the best of the authors’ knowledge, this is the first study to investigate the influence of bank ESG activities on their profitability and stability in OIC countries. The authors also extend the theoretical literature by connecting competition and regulatory quality to ESG-led financial performance.