Auditing is a collective process conducted by a professional accounting team with a wide range of skills and experience. Audit work is labor-intensive, and audit team diversity, particularly gender diversity, is considered to have both auditing and economic effects. However, there is scant empirical research on the way that audit engagements are conducted and the role of audit team leaders (ATLs), specifically female ATLs, in the audit effort, because they and other audit team members mainly develop audit strategies in practice during the planification period. A hand-collected private data set was gathered from Spanish small and medium-sized audit firms from 2001 to 2015. After controlling for endogeneity, the analysis shows a more efficient audit effort by female ATLs and their audit teams when task complexity increases. Furthermore, the findings show a masculinization process by female ATLs when their experience rises, which may be interpreted as intrinsic motivation for future promotions. Additional analyses also reveal differences in female ATLs’ behavior when there are shorter audit firm tenures and larger audit firm sizes. Overall, our empirical evidence is in line with the idea that gender diversity is positive for audit efficiency. Our study responds to calls from regulators to consider audit team attributes as a relevant factor in the quality of audit quality practices.