Audit quality is an issue of great concern in dealing with the confidence and credibility crisis that has engulfed the investment scene following collapse of many firms around the world as a result of outright fraud or fraudulent financial reporting. The study used panel data approach to investigate determinant of audit quality of firms listed in Nigerian Stock Exchange. Positivist research paradigm and Ex post facto research design was adopted. Thus secondary data was collected from sample of 14 firms purposively selected from non-financial firms from 2012 to 2019 resulting to 112 firm specific observations. Audit quality measured by accrual quality developed by Dechow and Dichev 2002 is the dependent variable. Audit fee, audit independence, audit switching, audit effectiveness (audit firm size) constitute the independent variables. Result of the study revealed that about eleven percent variation in the audit quality of sampled firms was jointly explained by the independent variables used in the study. The beta coefficient of the variables showed that audit fee, audit independence, audit switching and audit effectiveness (audit firm size) is negative but not significant in influencing accrual level. This indicates that the independent variables by reducing accrual level increases audit quality. The study concluded that audit fee, audit independence, audit switching and audit effectiveness by reducing accrual level has positive but insignificant effect on audit quality of selected firms. The study affirms Agency theory that managers opportunistic behaviour can be reduced by a third party employed by the owners. The study among other things recommended that firms should review their policies particularly as it concerns their external auditors to ensure that there are no familiarity threats, real or perceived conflict of interest that will undermine their independence in carry out their services. there is also need to enforce recent regulations toward audit firm rotation or switching after the ten years' period specified in the 2018 Code of corporate governance in order to reduce information risk and enhance audit quality.