In the course of fulfilling public duties, the government has lawfully collected a vast amount of data related to socioeconomic development. Fully unlocking the value of this public data is of great importance for promoting the integration of the digital and real economies. Based on a panel dataset of A-share listed companies in China from 2012 to 2022, this study employs a difference-in-differences (DID) model to examine the impact of public data openness (PDO) on corporate green investment (GI). The empirical results show that PDO significantly enhances the level of green investment by Chinese firms, highlighting the effectiveness of digital information disclosure as a soft regulatory tool for promoting corporate environmental behavior. The study further finds that the effect of PDO is more pronounced in regions with a lower degree of marketization. Additionally, the positive impact of PDO on green investment is stronger for heavily polluting firms, suggesting that companies facing greater regulatory and reputational pressure respond more actively to environmental information disclosure. This study provides new evidence on the role of PDO in advancing corporate sustainability practices and underscores the importance of designing differentiated policies based on institutional and industry contexts.