In recent years, more and more research has focused on the impact of corporate social responsibility (CSR) on business activities. Due to the existence of two different theoretical perspectives, shareholder value theory and managerial opportunism theory, the research on CSR has reached different conclusions. Meanwhile, the motivations for environmental investments in enterprises have received attention from scholars. However, there is a lack of empirical research on the relationship between CSR and environmental investment. Therefore, this study conducts a regression analysis on the external evaluation of CSR and enterprises’ environmental investment using data from Chinese listed companies. The empirical results show a significant positive relationship between the external evaluation of CSR and enterprises’ environmental investment. The mediating tests conducted based on information transmission and resource acquisition mechanisms explain the reasons for this promotion effect, supporting the shareholder value theory. Furthermore, our research finds that this promotion effect is more significant in non-state-owned enterprises, enterprises receiving fewer environmental subsidies, enterprises disclosing environmental philosophies, and enterprises identified as key pollution-monitoring units in reports. The research findings of this study are meaningful for clarifying the economic consequences of CSR and provide practical evidence for Chinese enterprises to understand the importance of environmental investment and the government’s advocacy for enterprises to proactively engage in environmental investment.