This study examines whether the decision to voluntarily (i.e. without a statutory obligation) employ two audit firms to conduct a joint audit is related to audit quality. We use separate samples and empirical designs for public and privately held companies in Sweden, where a sufficient number of companies have a joint audit on a voluntary basis. Our empirical findings suggest that companies opting to employ joint audits have a higher degree of earnings conservatism, lower abnormal accruals, better credit ratings and lower perceived risk of becoming insolvent within the next year than other firms. These findings are robust to the use of a propensity score matching technique to control for the differences in client characteristics between firms that employ joint audits and those that use single Big 4 auditors (i.e. auditor self-selection). We also find evidence that the choice of a joint audit is associated with substantial increases in the fees paid by the client firm, suggesting a higher perceived level o...