Unfair low-price competition hinders the provision of high-quality audit services and impairs the sustainable and healthy development of the audit industry. This paper constructs a quasi-natural experiment based on the institutional change in audit fees regulation in China from 2008 to 2019. It compares audit opinion shopping across the pre-implementation, implementation, and post-implementation periods of audit fee regulation, and then uses the difference-in-difference approach to examine the impacts of audit fees regulation on audit opinion shopping. Our findings reveal that, compared with the implementation-period of audit fees regulation, the likelihood of audit opinion shopping is significantly higher in both the pre-implementation and the post-implementation periods, suggesting that audit fees regulation can mitigate audit opinion shopping to a certain extent. In addition, the mitigating effect of audit fees regulation on audit opinion shopping is more pronounced for firms audited by non-BIG10 audit firms. Furthermore, our findings are still robust after a variety of sensitivity tests and after controlling for potential endogeneity issues. Lastly, the negative association between audit fees regulation and audit opinion shopping is more pronounced for firms with strong audit industry supervision and firms in regions with lower marketization indexes. This study enriches the existing literature on audit fees regulation, providing an important reference for China’s audit policy-making.