["Business Ethics, the Environment &Responsibility, EarlyView. ", "\nABSTRACT\nThis study examines the effect of the Women Leadership Index (WLI) on sustainability reporting assurance and the assurance level selected. The sample comprises 1781 non‐financial firms across Asia‐Pacific, Europe, and the Middle East & Africa over the period 2016–2023, yielding 13,107 firm‐year observations. The analysis employs ordinal logistic regression, and the results remain robust after a series of robustness and endogeneity tests. The findings reveal that the Women Leadership Index (WLI) increases the likelihood that firms adopt sustainability reporting assurance and encourages the selection of higher assurance levels (i.e., reasonable assurance). These results suggest that the quality of female board members, reflected in the integration of gender, education, and experience, strengthens external monitoring functions and enhances the credibility of sustainability reporting. This study provides important implications for firms and regulators by emphasizing the need to consider not only female representation but also the human capital quality of women on boards. Furthermore, it extends the application of the WLI to the context of sustainability reporting assurance by providing international evidence that the quality of female board members plays a significant role in firms' decisions to engage in external verification of sustainability reports.\n"]