Regulators have been greatly concerned about the lack of competition in the audit market due to its potential effects on audit fees and quality. However, a consensus has not yet been made on how competition affects auditors’ behavior. Using the number of auditors (audit offices) located in the local area as a proxy for audit market competition, we re-examine the controversy. Our empirical results reveal the following. First, we find that the frequency of auditor turnover increases with the number of auditors operating in a local area, suggesting that a greater number of auditors intensify competition among auditors in the local audit market. Second, both audit fees and quality decrease with the number of auditors. Third, the aforementioned effects are mainly driven by the number of non-Big 4 auditors rather than by the number of Big 4 auditors. Fourth, such effects do not exist in the market segment with extremely large clients who demand audits exclusively from Big 4 auditors. However, in the other segment with small and medium-sized clients, both Big 4 and non-Big 4 auditors are affected by the number of auditors. These findings provide regulators and many other interested parties with valuable insights into the effect of audit market structure on auditor behavior.