This paper examines the impact of urbanization on CO2 emissions in developing countries, focusing on the heterogeneity of the relationship across different income levels. The study uses a panel data model to decompose emissions data into scale, composition, and technique effects. The results show that while population growth has a positive and above-unitary elasticity on emissions for all income groups, urbanization has a more complex effect. For low and lower-middle-income countries, the elasticity of emissions with respect to urbanization is higher than unity, indicating a strong positive impact. In contrast, for upper-middle-income and highly developed countries, the elasticity is negative, suggesting a reduction in emissions as urbanization reaches a certain level. The findings highlight the importance of considering the heterogeneous impact of urbanization on CO2 emissions in climate change policies.This paper examines the impact of urbanization on CO2 emissions in developing countries, focusing on the heterogeneity of the relationship across different income levels. The study uses a panel data model to decompose emissions data into scale, composition, and technique effects. The results show that while population growth has a positive and above-unitary elasticity on emissions for all income groups, urbanization has a more complex effect. For low and lower-middle-income countries, the elasticity of emissions with respect to urbanization is higher than unity, indicating a strong positive impact. In contrast, for upper-middle-income and highly developed countries, the elasticity is negative, suggesting a reduction in emissions as urbanization reaches a certain level. The findings highlight the importance of considering the heterogeneous impact of urbanization on CO2 emissions in climate change policies.