Purpose–Thispaperaimstoexaminehowleadershipstyleinauditfirmsinfluencesauditquality.The paper further exploresthemediatingroleofknowledgesharingintherelationshipbetweenleadershipstyleandaudit quality. Design/methodology/approach– The present paper studies the effects of transformational and servant leadership styles on audit quality through knowledge sharing. Data are collected from 396 Iranian external auditors via a questionnaire. Findings– The results show that both transformational and servant leadership style significantly influence auditqualitythroughknowledgesharing.Moreover,theimpactoftransformationalleadershipstyleisstronger than the impact of servant leadership style. Originality/value– In audit quality literature, little attention has been devoted to both leadership style and knowledge sharing. This paper develops a parsimonious model which shows how leadership style improves audit quality, and how knowledge sharing strengthens the impact of leadership style on audit quality. The results have important implications particularly for audit industry.