["Corporate Social Responsibility and Environmental Management, Volume 33, Issue 3, Page 4134-4152, May 2026. ", "\nABSTRACT\nThis study explores the relationship between six heterogeneous classifications of institutional ownership (IO) and corporations' biodiversity disclosure. From a theoretical perspective, we use legitimacy and institutional theories. The study relies on panel data with observations pertaining to corporations whose headquarters are located in Europe, covering the 2019 to 2023 fiscal years. In line with the theoretical frameworks and the results gathered from several regression analyses and robustness checks, we found that foreign IO and cross holdings IO have a significant and negative effect on firms' biodiversity disclosure. Whereas, financial IO and government IO have a positive and significant effect. Finally, pension fund IO has a non‐significant effect on corporations' biodiversity disclosure. To the best of our knowledge, this is the first empirical study exploring the link between a granular and heterogeneous classification of IO and corporations' biodiversity performance, thereby providing useful insights for both theory and practice.\n"]