<p>This study uses rapidly urbanizing China as a case study to explore the effects of urban sprawl on carbon emissions and the underlying mechanisms; then, this study conducts an empirical test using urban panel data from 2002 to 2023. The results show that urban sprawl significantly increases carbon emissions in general. This study further finds that urban sprawl affects carbon emissions through three main pathways. First, urban sprawl promotes industrial expansion, which increases industrial carbon emissions and thus increases overall carbon emissions. Second, urban sprawl fosters the prosperity of real estate development and construction, which not only improves direct carbon emissions but also further increases indirect carbon emissions by promoting the development of heavy industries, such as steel and cement. Third, urban sprawl increases carbon emissions by increasing the reliance on small car trips and decreasing the share of public transportation trips. The effect of urban sprawl on carbon emissions is stronger in the central and western regions and in small and medium-sized cities than in the eastern region and large cities. In terms of period, the impact of urban sprawl on carbon emissions had a greater influence before the Copenhagen Conference, when China made its commitment to reduce emissions.</p>