Urban land use change has the potential to affect local to global biogeochemical carbon (C) and nitrogen (N) cycles and associated greenhouse gas (GHG) fluxes. We conducted a meta-analysis to 1) assess the effects of urbanization-induced land-use conversion on soil nitrous oxide (N₂O) and methane (CH₄) fluxes, 2) quantify direct N₂O emission factors (EF_d) of fertilized urban soils used e.g., as lawns or forests, and 3) identify the key drivers leading to flux changes associated with urbanization. On average, urbanization increases soil N₂O emissions by 153%, to 3.0 kg N ha^-1 yr^-1, while rates of soil CH4 uptake are reduced by 50%, to 2.0 kg C ha^-1 yr^-1. The mean annual N₂O EF_d of fertilized lawns and urban forests is 1.4%, suggesting that urban soils can be regional hotspots of N₂O emissions. On a global basis, conversion of land to urban greenspaces has increased soil N₂O emission by 0.46 Tg N₂O-N yr^-1 and decreased soil CH₄ uptake by 0.58 Tg CH₄-C yr^-1. Urbanization-driven changes in soil N₂O emission and CH4 uptake are associated with changes in soil properties (bulk density, pH, total N content and C/N ratio), increased temperature, and management practices, especially fertilizer use. Overall, our meta-analysis shows that urbanization increases soil N₂O emissions and reduces the role of soils as a sink for atmospheric CH₄. These effects can be mitigated by avoiding soil compaction, reducing fertilization of lawns, and restoring native ecosystems in urban landscapes.