This paper investigates the impact of ownership and ownership concentration on the performance of China’s listed firms. By recognizing the differences between ownership and ownership concentration and between total ownership concentration and tradable ownership concentration, we conduct simplex, interactive and joint analyses. We find that ownership concentration is approximately associated with higher firm performance. Ownership concentration is more powerful than any category of ownership in determining firm performance. Firm performance is better when the state is the largest of the top shareholders and/or institutions dominate ownership among the top tradable shareholders. Our results support the theory that high ownership concentration mitigates the agency problem.