The present research endeavors to examine the moderating effect of firm size on the relationship between the tenure of the audit committee chair and the board of directors with sustainability disclosure. Data from 592 non‐financial firms listed on the ASE from 2014 to 2021 were analyzed. The findings indicated that a longer tenure of a board of directors leads to increased sustainability disclosure, and firm size positively moderates this relationship. Moreover, the research outcomes indicated that the audit committee chair tenure had a positive yet non‐significant correlation with sustainability disclosure, with no moderating effect of firm size on this relationship. This study provides valuable insights for stakeholders, including investors, managers, and regulators, particularly in developing economies, by demonstrating the influence of corporate governance (CG) on sustainable development. The examination of firm size as a moderating factor offers a unique contribution to the existing literature, thus providing a deeper understanding of the indirect impact of CG on sustainability reporting.