This study examines the relationship between environmental, social, and governance (ESG) disclosure quality and analyst forecast accuracy for firms listed on the Nigerian Exchange Group (NGX) over the period 2011–2025. Using an ex-post facto research design and panel regression analysis on an unbalanced sample of 148 listed firms, we construct a composite ESG disclosure quality index based on the Global Reporting Initiative (GRI) standards, NGX Sustainability Disclosure Guidelines, and the Nigerian Code of Corporate Governance 2018. Our findings reveal that higher ESG disclosure quality is significantly and positively associated with analyst forecast accuracy, suggesting that transparent and comprehensive sustainability reporting reduces information asymmetry between corporate managers and external information intermediaries. The relationship remains robust after controlling for firm size, leverage, liquidity, asset tangibility, sales growth, firm age, earnings volatility, natural risk management, industry classification, risk exposure, and year fixed effects. Post-estimation diagnostics, including the Hausman test, Wooldridge test for autocorrelation, Pesaran CD test for cross-sectional dependence, and modified Wald test for groupwise heteroskedasticity, confirm the appropriateness of the fixed-effects model with Driscoll-Kraay standard errors. The study contributes to the limited but growing body of literature on ESG disclosure in frontier and emerging African markets, offering timely insights as Nigeria transitions from voluntary to mandatory sustainability reporting under the Financial Reporting Council's roadmap for International Sustainability Standards Board (ISSB) adoption. For policymakers, the findings underscore the capital market benefits of enforcing standardized ESG disclosure regimes. For corporate managers, the results provide empirical justification for investing in high-quality sustainability reporting infrastructure.