<p>Sustainable urbanization (SU) has received increasing attention due to global economic, social, and environmental issues. Advancing SU will help transform to a low-carbon future and reduce the global greenhouse effect. This study uses panel data from 119 countries spanning 2001 to 2020, utilizing an improved entropy method to construct a comprehensive SU index that integrates economic, social, and environmental dimensions. To assess the impact of SU on per capita carbon dioxide emissions (CO₂), the study employs the STIRPAT model and system generalized method of moments model. The key findings are as follows: (1) SU is negatively correlated with per capita CO₂ globally; (2) the impact of SU on emissions varies regionally, with significant reductions observed in non-Organization for Economic Co-operation and Development (OECD) countries, while the effect is negligible in OECD countries; and (3) the proportion of renewable energy in power generation mediates the relationship between SU and emissions. Policy recommendations emphasize accelerating electrification and renewable energy adoption, enhance investment in sustainable infrastructure, and design region-specific strategies to advance sustainable urbanization and mitigate climate change.</p>