PurposeThe purpose of this paper is to investigate the effects of corporate governance mechanisms, namely, board of directors and auditors, on tax aggressiveness in Italian companies listed on the Milan Stock Exchange.Design/methodology/approachThis study used a population of 168 Italian non-financial firms listed on the Milan Stock Exchange, holding shares in at least one foreign subsidiary in countries other than Italy in fiscal year 2018. Data on corporate boards and auditors were collected through the evaluation of companies’ annual reports over the period 2011–2018. Five panel data analyses with fixed effects were performed for each tax aggressiveness index, yielding 1,176 observations to test the research hypothesis.FindingsThis paper finds that corporate board characteristics, such as size, gender diversity and CEO duality, and auditors’ features, such as external audit quality, increase corporate tax aggressiveness.Practical implicationsThis study provides investors with an understanding of corporate boards’ and auditors’ roles in preventing agency conflicts and evaluating a company’s tax approach. Furthermore, the findings are useful for international political bodies in regulating corporate board composition and managerial monitoring.Originality/valueAlmost all studies focusing primarily on corporate governance mechanisms’ effects on tax aggressiveness are within the US context. Empirical evidence on the topic in the European contexts is limited. The legislative discrepancy between countries is reflected in the computation of indices measuring tax aggressiveness, affecting US studies' generalizability across nations. This paper extends the literature on the topic by investigating other unexplored corporate governance mechanisms. Five indices were used to measure corporate tax aggressiveness and to assess analysis reliability and data robustness. Moreover, to the best of the authors’ knowledge, this study is the first attempt to investigate the link between corporate governance mechanisms and tax aggressiveness in Italy.