This paper examines whether internal control can mitigate the negative impact of auditor-executive hometown ties on audit quality using a sample of A-share listed companies from 2014 to 2020. The findings suggest that audit quality decreases when there is a hometown ties between auditors and executives. However, when corporate internal control quality improves, the negative impact of hometown ties on audit quality decreases significantly. Further analysis reveals that internal control does not directly reduce the probability of hometown auditor, but rather inhibits the negative impact of the relationship after the hometown auditor is appointed. From the perspective of internal control’s five elements, those of internal environment, information & communication, as well as supervision are more prominent in inhibiting the negative impact of the hometown ties. Finally, this paper finds that whether internal control can play a restraining role also depends on the extent they are implemented. Internal controls are shown to be more effective in non-state listed companies and in companies with less controlling shareholders power. This study helps to deepen the understanding of how internal control plays an important role in mitigating the negative effects of informal systems.