• Manuel Delgado-Baquerizo, 
• Pablo García-Palacios, 
• Mark A. Bradford, 
• David J. Eldridge, 
• Miguel Berdugo, 
• Tadeo Sáez-Sandino, 
• Yu-Rong Liu, 
• Fernando Alfaro, 
• Sebastian Abades, 
• Adebola R. Bamigboye, 
• Felipe Bastida, 
• José L. Blanco-Pastor, 
• Jorge Duran, 
• Juan J. Gaitan, 
• Javier G. Illán, 
• Tine Grebenc, 
• Thulani P. Makhalanyane, 
• Durgesh Kumar Jaiswal, 
• Tina U. Nahberger, 
• Gabriel F. Peñaloza-Bojacá, 
• Ana Rey, 
• Alexandra Rodríguez, 
• Christina Siebe, 
• Alberto L. Teixido, 
• Wei Sun, 
• Pankaj Trivedi, 
• Jay Prakash Verma, 
• Ling Wang, 
• Jianyong Wang, 
• Tianxue Yang, 
• Eli Zaady, 
• Xiaobing Zhou, 
• Xin-Quan Zhou 
• César Plaza 

Urban greenspaces support multiple nature-based services, many of which depend on the amount of soil carbon (C). Yet, the environmental drivers of soil C and its sensitivity to warming are still poorly understood globally. Here we use soil samples from 56 paired urban greenspaces and natural ecosystems worldwide and combine soil C concentration and size fractionation measures with metagenomics and warming incubations. We show that surface soils in urban and natural ecosystems sustain similar C concentrations that follow comparable negative relationships with temperature. Plant productivity’s contribution to explaining soil C was higher in natural ecosystems, while in urban ecosystems, the soil microbial biomass had the greatest explanatory power. Moreover, the soil microbiome supported a faster C mineralization rate with experimental warming in urban greenspaces compared with natural ecosystems. Consequently, urban management strategies should consider the soil microbiome to maintain soil C and related ecosystem services.