Whether semi-urbanization can effectively help reduce carbon emissions has become increasingly attractive to scholars and policymakers. To the knowledge of the authors, there are no empirical studies that were conducted to explore the impact of semi-urbanization on carbon emissions from a spatial perspective. By employing panel data for the years between 2000 and 2014 of 30 Chinese provinces, this paper examines the relationship between semi-urbanization and carbon emissions by using a spatial regression method. Also, the spatial transmission mechanisms between semi-urbanization and carbon emissions are analyzed. Empirical results indicate a positive spatial spillover effect on carbon emissions across various regions. Simultaneously, we find that semi-urbanization not only facilitates emission reduction in a particular region, but also significantly reduces the carbon emissions in surrounding regions, ultimately implying a significant and negative total effect. Moreover, semi-urbanization has decreased carbon emissions, that is, for every 1% increase in semi-urbanization, the carbon emissions will decrease by 0.803%. Furthermore, semi-urbanization, industrial structure, technological progress, human capital, and energy consumption show spillover impacts on carbon emissions, yet their impact mechanisms vary substantially across various regions. Based on these findings, we suggest several related policy implications for mitigating carbon emissions and promoting semi-urbanization in China.