This study aimed at examining the impact of environmental accounting disclosure (EAD) on manufacturing companies’ financial reporting and performance and to assess the degree of EAD in selected manufacturing firms. The study adopted descriptive statistics and ex-post facto research design using secondary data from ten manufacturing firms listed on the Nigerian Exchange Group (NGX) that publish sustainability or environmental reports. The sample was selected using purposive sampling and data were analysed using simple linear regressions. Results showed a significant positive relationship between environmental accounting disclosure and return on assets, β = 6.78, t(8) = 3.77, p = .006, R² = .64, meaning that firms with higher levels of environmental disclosure tend to record stronger asset utilisation and profitability; a statistically significant effect of EAD on net profit margin, β = 18.35, t(8) = 3.69, p = .007, R² = .62, which implied that greater disclosure of environmental information aligns with higher profit margins; and that environmental disclosure significantly predicted earnings per share, β = 6.44, t(8) = 3.72, p = .007, R² = .63, implying improved market confidence and valuation as investors may reward transparent environmental reporting. The study therefore concluded that environmental accounting disclosures have a significant positive impact on the corporate financial reporting of manufacturing firms in Nigeria, as firms with higher disclosure levels demonstrate stronger profitability and improved financial reporting quality. It was recommended that Financial Reporting Council of Nigeria, SEC and NGX should make environmental disclosure mandatory for all listed firms to improve consistency and comparability while manufacturing firms should adopt internationally recognised frameworks such as GRI and ISSB to strengthen the credibility of sustainability reporting.