Understanding the profound impacts of urban shrinkage on local carbon emissions is important for implementing sustainable development strategies. This study attempts to examine the effects of urban shrinkage on carbon emissions from local households. By combining emission data in the household sector, urban population, and socioeconomic indicators at the municipal level in Japan, we construct a panel dataset for further analysis. Firstly, the depiction of typical facts presents spatial differences in carbon emissions. Secondly, using panel regression based on a two-way fixed model, we find that urban shrinkage resulting from population loss has an adverse impact on carbon emissions from households locally. In addition, heterogeneous analysis indicates that the severity of this effect is greater for larger cities and towns, and villages. Finally, we also address the mechanisms behind the latent factors at work here; the higher carbon emissions per household in shrinking cities are driven by the decreasing household size, aging population, and lower household installation of renewable energy equipment in the city. The findings of this study have significant implications for urban governance and policy formulation directed toward following the decarbonization path.