This research examines the transformation of directors' fiduciary duty doctrine in responding to environmental sustainability demands (green corporate governance) through a comparative legal study of Indonesia and Malaysia. Employing normative juridical comparative methods with statute approach and comparative approach, this study finds that Indonesian company law still interprets fiduciary duty conventionally based on shareholder primacy, while Malaysia has more progressively integrated sustainability dimensions into directors' duty standards through the Companies Act 2016, Malaysian Code on Corporate Governance 2021, and Bursa Malaysia's mandatory sustainability reporting framework. This research argues that legal reconstruction through amendment of Law Number 40 of 2007 on Limited Liability Companies, adopting an ESG-oriented enlightened shareholder value model, is a juridical imperative to achieve sustainable corporate governance in Indonesia.