This paper investigates the relationship between two characteristics of corporate governance (concentrated and state ownership) and firm financial performance by bringing new and extensive evidence from an emerging market. Further, this study examines the impact of the recent stock split reform in China on the corporate ownership characteristics–firm performance relationship. The final sample of this study is comprised of 234 firms with 2340 annual observation values. The study hypotheses are examined using regression analysis of panel data. We found that concentrated ownership is positively and significantly related to firm performance. However, state ownership has a significant negative impact on firm performance. Further, we observed that the stock split reform has a substantial and positive effect on the ownership–corporate financial performance relationship. In particular, the positive relationship between ownership concentration and firm performance has increased following the split-share structure reform. The negative relationship between state ownership and corporate financial performance has been mitigated following the split-share structure reform. We contribute to the existing literature on corporate governance by investigating the ownership–corporate financial performance relationship in a unique research setting based on the impact of an exogenous regulatory change, namely, the split-share structure reform in China. The study presents implications for regulators, investors, and researchers interested in examining developing markets such as China. Our results imply that the institutional reform of the Chinese stock market has benefitted investors through enhancing corporate financial performance. The findings suggest that the reform of the Chinese stock market has significantly shaped the impact of ownership structure on corporate financial performance in a valuable way for effective capital allocation. Thus, collectively, the split-share structure reform enhances the quality of corporate governance, which is pivotal to the growth of the country’s economy. This, in turn, has policy implications for other emerging economies.