Prior research on investor reactions to earnings announcements has shown that the institutional setting significantly influences the information content of these announcements (e.g. DeFond, Hung, & Trezevant, 2007). However, this literature does not consider the role of firm-specific governance mechanisms and the role they play in enhancing earnings credibility. We posit that governance mechanisms such as independent audit committees have a significant influence on earnings credibility and that this relationship varies across institutional settings. Specifically, we show that audit committees play an especially important role in enhancing earnings credibility in countries with weaker accounting standard enforcement, or weaker legal protection of investors. As such we are the first to investigate the joint effect of firm-level governance mechanisms, such as the audit committee, and the institutional context on earnings credibility. The European setting provides a unique opportunity to investigate investor perception of audit committee effectiveness in various institutional contexts. Since 2006, European public-interest entities1 must establish an audit committee that includes at least one independent member (European Commission, 2006). Some companies, however, have voluntarily decided to hire 100% of independent members on the audit committee, which ultimately results in large disparities in the composition of European audit committees. Such variance does not exist anymore in the US, because the Sarbanes-Oxley Act obliges public firms to appoint 100% of independent members in the audit committee. In 2014, the European legislation was amended. The European commission decided that at least half (50%) of the members sitting on the audit committee must be independent. This new regulation, which entered into force in 2016, does not affect our study that covers the period 2006–۲۰۱۴٫ This study focuses on investor reactions to annual earnings announcements, which crucially depends on the credibility of the earnings. Indeed, investors must believe that earnings reflect the true performance of the company, which is notably the case when managers (or insiders) have not managed earnings (Dechow, Ge, & Schrand, 2010; Healy & Wahlen, 1999; Leuz, Nanda, & Wysocki, 2003). Since the credibility of earnings is not directly observable, investors may try to assess it by focusing on some observable factors. First, institutional characteristics may improve the credibility of earnings, such as the legal protection of investors (Ball, Kothari, & Robin, 2000; Leuz et al., 2003).