["Business Strategy and the Environment, Volume 35, Issue 5, Page 6691-6714, July 2026. ", "\nABSTRACT\nThis study employs hierarchical regression modelling on a survey of 550 firms from Nigeria and Ghana to examine the impact of sustainability auditing on corporate governance, environmental performance, and financial outcomes of high‐impact industries. Our findings reveal that internal sustainability auditing significantly enhances environmental performance, regulatory compliance, corporate governance transparency, and accountability. Additionally, external sustainability auditing positively influences firms' financial performance and long‐term value. Notably, we identify cross‐country variations: Internal sustainability auditing has a stronger effect on environmental performance and corporate governance in Ghana, whereas external audits exhibit a greater impact on financial performance and long‐term firm value in Nigeria. Moreover, industry‐specific insights indicate that internal audits are particularly influential in improving environmental performance within the mining sector while they play a critical role in strengthening corporate governance within the oil and gas industry. The study underscores the importance of sustainability auditing in corporate governance frameworks for promoting environmental and financial sustainability in high‐impact industries, providing valuable insights for policymakers and corporate leaders.\n"]