This paper investigates the impact of industrial agglomeration on corporate carbon emissions in China. We measure the extent of industrial agglomeration utilizing distance-based continuous spatial measurement, differentiating between the quantity and scale of agglomeration. Using a panel of 7895 firm-year observations from 2007 to 2019, our findings indicate that regional industrial agglomeration contributes to a reduction in carbon emissions for firms located within those regions. Specifically, this reduction is primarily achieved through the alleviation of corporate financial constraints. We demonstrate that industrial agglomeration facilitates firms in accessing informal finance (e.g., trade credit) more effectively than formal finance (e.g., bank loans). Additionally, we find that the effect of industrial agglomeration on reducing carbon emissions is more pronounced for firms with higher environmental responsibility, while it is diminished in regions with greater marketization. The carbon reduction effect is also more significant for heavily polluting firms and those situated in areas with stricter environmental regulations. Furthermore, our study reveals that the implementation of green credit policies may weaken the carbon reduction effect of agglomeration by limiting access to financial resources. The robustness of our main results is confirmed through the Bartik-IV test and other robustness checks. Taken together, our findings suggest that industrial agglomeration can effectively lower corporate carbon emissions by easing financial constraints, offering valuable insights into strategies for enhancing corporate environmental performance.