Environmental, Social, and Governance (ESG) considerations are now firmly embedded in corporate governance discourse, yet their legal integration into directors’ fiduciary duties remains uneven and contested across jurisdictions. This article undertakes a comparative doctrinal analysis of how ESG regulation intersects with directors’ duties in the European Union, the United Kingdom, and the United Arab Emirates. Drawing on legislation, regulatory instruments, case law, and policy developments, the study examines the extent to which ESG obligations are translated into enforceable fiduciary responsibilities and the mechanisms through which boards are expected to address sustainability risks and impacts. The analysis reveals a fragmented regulatory landscape. The European Union has adopted a prescriptive, disclosure- and due-diligence-driven framework through instruments such as the Corporate Sustainability Reporting Directive and the proposed Corporate Sustainability Due Diligence Directive, while stopping short of imposing uniform director-level sustainability duties. The United Kingdom continues to rely on a principles-based model anchored in section 172 of the Companies Act 2006, leaving considerable discretion to directors despite growing pressure for statutory reform. The United Arab Emirates has pursued a rapidly evolving, market-led approach focused on mandatory sustainability reporting and financial governance reforms rather than explicit fiduciary obligations. The article argues that this divergence creates legal uncertainty for boards operating across borders and limits the effectiveness of ESG integration into corporate decision-making. It concludes that clearer legislative guidance, whether through refined statutory duties or strengthened soft-law instruments, is necessary to align directors’ responsibilities with contemporary sustainability expectations while preserving appropriate managerial discretion..