<p>Through the application of digital technology, e-government becomes a new government model for improving carbon emission efficiency and leading the economy towards a more sustainable direction. Based on the super-efficiency slack-based measure model with undesired output, this study measured the total-factor carbon emission efficiency (TCEE) of 136 countries during 2010–2020 and adopted the two-way fixed effects model and U-test methods to investigate the nonlinear impact of e-government on TCEE. The results are as follows. First, the average TCEE is increasing, with large differences among countries. Second, e-government has a significant nonlinear U-shaped effect on TCEE that first inhibits and then promotes. Meanwhile, there is also a significant U-shaped relationship between e-government and carbon emission intensity. Third, the impact of e-government on TCEE is heterogeneous due to different economic and urbanization levels. At the national scale, developing countries and countries with urbanization rates higher than 50% benefit more from the improvement of e-government. Fourth, the impact of e-government on TCEE is mainly achieved through its impact on improving energy structure and reducing energy intensity. Fifth, further analysis shows that the online service index and telecommunications infrastructure index also have a significant U-shaped impact on TCEE. This study enhances the understanding of the public environmental value of e-government and provides policy reference for the government to plan the development of e-government and protect the environment to achieve low-carbon development goals.</p>