Purpose – This paper investigates in the relationship between the audit firm factors; i.e., planning, supervision, specialization in the industry, and audit firm size and audit quality. This study examines the moderating effect of the external environment audit i.e., professional bodies, laws and regulations, and recognized standards in the relationship between audit firm factors and audit quality. Design/methodology/approach – The sample comprises the external auditors from Libyan Association of Accountants and Auditors (LAAA). Data was collected 253 auditors by personally administered questionnaire. Multiple regression analysis is applied to examine the association between audit office factors and external environment audit, and audit quality. Findings – The regression analysis supported a postulate that the audit firm factors have significant positive relationship with the audit quality. But the results indicate that the external environment audit factors cannot moderate the relationship between the audit firm factors and audit quality. Originality/value – This is the first study examining the impact of external environmental factors moderating between audit firm factors and audit quality.