China is an important emerging economy, and its capital market has witnessed rapid development in recent years. At the same time, market pressure and exposed risks have increased significantly, which might negatively influence entrepreneurial behaviors. From the perspective of behavioral finance, this study explored the impact of managers’ overconfidence on entrepreneurship, by analyzing mergers and acquisitions (M&As) of listed firms. Empirical studies were performed on listed Chinese firms by constructing a comprehensive index to measure managers’ overconfidence. The results show that overconfidence, which might promote the chance to exploit the business opportunities of M&As, has a negative impact on both, innovation entrepreneurship and profitability, after the M&A. Propensity score matching was also performed for possible sample selection bias, and the results support the same findings.