The rapid development of the digital economy is a critical national strategy for the Chinese government, with the establishment of digital economy platforms as a key component. Simultaneously, both the government and enterprises have embraced the concept of sustainable development. Since corporate environmental, social, and governance (ESG) performance serves as a crucial micro-indicator of sustainability, it is essential to investigate whether the digital economy platforms developed by the Chinese government can enhance the ESG performance of relevant companies. This paper first examines the impact of urban digital economy platform construction on corporate awareness of ecological and environmental protection, social responsibility, and governance practices. It then proposes two primary mechanisms—technological innovation and business model innovation. Finally, empirical evidence is presented based on a sample of 107 urban CSI 300-listed companies in China, using data from 2015 to 2019. The analysis yields three key findings: (1) the construction of urban digital economy platforms significantly improves the ESG performance of companies in the region; (2) the impact on the social subindex is not significant, but the effect is more pronounced in non-state-owned enterprises, the manufacturing sector, and the eastern region; and (3) business model innovation plays a more significant role in driving ESG performance compared to technological innovation. This study contributes to the understanding of how digital economy platforms influence corporate ESG performance.