ESG is an important standard for the international community to measure the green and sustainable development of enterprises. In the context of rapid development of FinTech, how technology empowerment can better help enterprises move towards a path of green and high-quality development has become one of the most important issues at present. Using data from A-share listed companies in Shanghai and Shenzhen from 2010 to 2022, this paper studies the impact of FinTech on corporate ESG performance and its underlying mechanisms. The results show that FinTech can significantly improve corporate ESG performance, including the overall ESG performance as well as individual E, S, and G performance. The impact mechanisms are that: First, FinTech can boost the internal growth of enterprises by upgrading their technology and reducing their agency costs, thereby improving their ESG performance. Second, FinTech can optimize the external environment of enterprises by reducing external transaction costs and alleviating financing constraints, thereby improving their ESG performance. Heterogeneity analysis indicates a more pronounced impact for financially disadvantaged, heavily polluting, and non-high-tech enterprises. From a macro perspective, the promoting effect of FinTech is more prominent in areas with weaker environmental regulations, lower bank competition, and limited marketization. Finally, the economic consequences show that the improvement of ESG by FinTech can further enhance corporate performance and alleviate operational risks. Based on the findings, this paper draws the following policy implications: First, heavily polluting enterprises should make full use of the technology spillover effect of FinTech to comply with the requirements of green development, improve ESG performance, and accelerate green transformation and upgrading in the context of the new era. Second, under the premise of stable development, we should fully unleash the empowering effect of FinTech, and expand its application and impact scope.