<p>Carbon emissions trading (CET) policies significantly affect enterprises’ financial performance, thus changing their low-carbon development strategies. In this study, a multitime point difference-in-differences model was used to identify the role and mechanism of the effect of CET on enterprises’ financial performance by taking Chinese A-share CET pilot enterprises from 2011 to 2021 as the sample. First, the CET has a negative effect on financial performance, and the effect is more significant in regions with a low degree of marketization. The results remain robust after passing the replacement core explanatory variable test, placebo test, and parallel trend test. The CET is still a challenge for improving financial performance. Enterprises need to go through a buffer period of cost digestion and strategic restructuring to adapt to CET. Second, technological innovation and financing constraints negatively regulate the relationship. Technological innovation can partially offset the policy impact by reducing the marginal cost of emission reductions, whereas financing constraints force enterprises to transform the pressure of CET compliance into an opportunity to improve resource efficiency. Finally, the CET has a negative impact on ESG performance, which in turn affects financial performance. The CET may lead to increased ESG management costs, providing a new perspective for understanding the complex consequences of environmental policies. The results indicate that improving the CET mechanism requires the coordinated promotion of technological innovation incentives, financing channel optimization, and ESG system construction. The study provides policy recommendations for the differentiated advancement of the national carbon market.</p>