A study synthesizes data from 420 observations across 257 cities in 52 countries to evaluate the global distribution of surface soil organic carbon (SOC) in urban greenspaces. The research finds that surface SOC density increases at higher latitudes and decreases with higher mean annual temperature, stronger temperature and precipitation seasonality, and lower urban greenness index. Using a random forest model, the study estimates an average SOC density of 55.2 Mg C ha⁻¹ and a total SOC stock of 1.46 Pg C in global urban greenspaces. The findings highlight the significant role of climate and urban greenness in shaping SOC density, with higher values observed in boreal regions compared to tropical areas. The study also reveals that urban greenspaces, despite covering a small fraction of global terrestrial surface SOC stocks, have high SOC density, suggesting potential for SOC accumulation. The results provide a baseline for future assessments of urban soil carbon under continued urbanization. The study underscores the importance of considering both natural and anthropogenic factors in understanding SOC dynamics in urban environments. It also highlights the need for further research to better understand the impacts of urbanization on SOC stocks and to develop management strategies for sustainable urban ecosystems.A study synthesizes data from 420 observations across 257 cities in 52 countries to evaluate the global distribution of surface soil organic carbon (SOC) in urban greenspaces. The research finds that surface SOC density increases at higher latitudes and decreases with higher mean annual temperature, stronger temperature and precipitation seasonality, and lower urban greenness index. Using a random forest model, the study estimates an average SOC density of 55.2 Mg C ha⁻¹ and a total SOC stock of 1.46 Pg C in global urban greenspaces. The findings highlight the significant role of climate and urban greenness in shaping SOC density, with higher values observed in boreal regions compared to tropical areas. The study also reveals that urban greenspaces, despite covering a small fraction of global terrestrial surface SOC stocks, have high SOC density, suggesting potential for SOC accumulation. The results provide a baseline for future assessments of urban soil carbon under continued urbanization. The study underscores the importance of considering both natural and anthropogenic factors in understanding SOC dynamics in urban environments. It also highlights the need for further research to better understand the impacts of urbanization on SOC stocks and to develop management strategies for sustainable urban ecosystems.