Governmental financial supervision is an important mechanism for improving accounting information quality and maintaining capital market order. Yet the large number of regulated firms and the limited scope of direct inspections raise a critical question: Will the governance effects of financial supervision extend beyond inspected firms through market-based channels? Taking the quality inspections of accounting information by the Ministry of Finance as the research setting, this paper examines whether governmental financial supervision spills over to non-inspected firms through common ownership networks formed by institutional investors.

Using manually-collected inspection data, institutional ownership data, and financial information on A-share listed companies from 2008 to 2024, this paper constructs a novel measure of firms’ exposure to financial supervision spillovers through common ownership. The results show that non-inspected firms more closely connected to inspected firms through common institutional investors exhibit significantly lower abnormal accruals, indicating improved accounting information quality. Further analysis shows that the spillover effect is mainly driven by institutional investors’ active monitoring, especially when they have stronger moni- toring incentives and longer holding horizons. The effect operates through active governance engagement, as higher exposure is associated with a greater likelihood of institutional investors appointing directors or senior governance personnel. It is also stronger in regions with higher marketization, weaker government intervention, and better transportation infrastructure, suggesting that monitoring costs shape the direction and strength of the spillover effect.

This paper extends research on governmental financial supervision from direct regulatory effects to network-based external spillovers and identifies common institutional investors as collaborative governance actors linking public supervision with market monitoring. Unlike studies emphasizing information intermediaries, this paper highlights how institutional investors transform regulatory signals and cross-firm comparisons into governance actions. The findings suggest that regulators can improve supervisory efficiency by considering firms’ network positions, enhancing inspection-result disclosure, and encouraging institutional investors’ gover- nance participation, thereby amplifying the effects of limited regulatory resources and improving information quality in the capital market.