Global biodiversity is declining at an unprecedented rate, and corporations in high-risk sectors such as plantations, utilities, and constructions play pivotal role in this trajectory. While biodiversity reporting has grown, much of it remain disclosure-driven, raising concerns that corporate transparency does not necessarily reflect measurable ecological outcomes. Responding to this concern, this study examines the disclosure-outcome gap by comparing corporate biodiversity reporting through two complementary lenses: the Global Reporting Initiative (GRI) disclosure framework and an outcome-oriented index inspired by the International Union for Conservation of Nature (IUCN). Nine leading Malaysian companies from biodiversity-sensitive sectors were chosen and their 2024 sustainability and integrated reports were analysed. A structured rubric assessing five pillars – reporting scope, biodiversity impacts, species protection, conservation outcomes, and governance, scored on a scale of 0 to 3, weighted and standardized to 100 points were used. Findings show plantation firms lead with relatively strong disclosure and outcomes due to external certification and NGO pressures. In contrast, utilities and contsructions companies report policies and governance structures but provide little evidence of measurable ecological results, creating significant gaps between GRI and IUCN scores. The study contributes a dual-index benchmarking approach that combines disclosure standards with conservation science. The results underscore the need for regulators such as Bursa Malaysia to mandate outcome-based biodiversity metrics and for firms to integrate scientific monitoring into sustainability strategies. Moving beyond symbolic compliance towards verifiable biodiversity outcomes is essential if corporate reporting is to meaningfully support conservation.