We investigate whether environmental, social and governance (ESG) transparency, the extent of ESG disclosure, has an impact on firm value. Reducing investors’ information symmetry and agency costs is the mechanism by which better ESG transparency potentially impacts firm value. Using Bloomberg ESG disclosure scores to assess a firm's ESG transparency, we look at a sample of 1996 large cap companies across 47 developed and emerging countries and territories. Our empirical analyses suggest that the benefits from ESG disclosure outweigh their costs for the average listed firm. We find supporting evidence for greater disclosure of ESG issues boosting firm valuation measures, such as Tobin's Q. Furthermore, our results suggest that firms with greater asset size, better liquidity, higher R&D intensity, fewer insider holdings and good past financial performance will be more transparent in ESG issues.