As the strictest environmental protection law in China's history, it is still unknown whether the New Environmental Protection Law (NEPL) can provide support for the low-carbon development of firms. This study employs the difference-in-differences (DID) model to analyze a sample of 3,525 firmyear observations in China from 2011 to 2019. The objective is to determine whether and under what circumstances the NEPL encourages firms to engage in CER. The empirical findings provide strong evidence that 1) the NEPL has notably improved the level of CER for heavily polluting enterprises, but the effect is attenuated over time; 2) for heavily polluting firms in regions with lower environmental regulation levels and non-state-owned heavily polluting enterprises, the effect of the NEPL is more pronounced; and 3) higher levels of public participation amplify the effect of the NEPL on heavily polluting firms’ CER. Our research significantly contributes to the understanding of the effect of the NEPL on CER, providing valuable insights that enrich the existing literature and have practical implications for environmental governance in China.