This paper aims to advance in the knowledge of the economic impacts of ISO 50001 certification on firms' performance. The study hypothesizes that ISO 50001 is associated with improvements in market value of firms. We employ, on one hand, event study methodology for a sample of 40 companies listed on different stock exchanges. On the other hand, we use market reaction to the announcement of ISO 50001 as a proxy for changes in firm performance. We reveal that market reaction to the adoption of ISO 50001 is negative but statistically insignificant. However, this result is not suggesting that getting ISO 50001 is a bad investment, but rather that inflated expectations of financial performance improvement due to the adoption of ISO 50001 has still been unfounded
