Prior empirical studies attempting to clarify the relationship between corporate environmental performance and financial performance have failed to reach clear conclusions due to methodological issues and limitations in environmental performance data. This study sought to complement existing research by demonstrating that firms with superior environmental management achieve better financial performance. Based on the premise that the effects of environmental management are expected in the long term rather than the short term, this study evaluated environmental performance over an extended period and analyzed its long-term impact on financial performance. Using data from the Economic Justice Research Institute under the Citizens' Coalition for Economic Justice, which evaluated corporate environmental performance from 1996 to 2000 (excluding 1998), this study analyzed the relationship between environmental performance and financial performance for 167 firms. The results revealed the following. First, firms that demonstrated good environmental performance during the evaluation period also experienced improved financial performance in subsequent periods. Additionally, good environmental performance during that period was found to have a positive (+) effect on the change in financial performance before and after the evaluation period. These results indicate that corporate investment in environmental management is accompanied by economic returns in the long run. Second, financial performance in the pre-evaluation period was found to have no effect on environmental performance during the evaluation period. This result implies that firms with good financial performance do not necessarily engage in proactive environmental management, thereby providing new empirical evidence supporting the claim that environmental performance influences financial performance. Therefore, the findings of this study suggest that environmental management can serve as an important strategic instrument for enhancing corporate value and performance in the long term.