Intensive management of urban lawns is globally widespread, predominantly for aesthetic reasons. However, a growing body of knowledge demonstrates negative ecological and environmental effects of this practice. We present a meta‐analysis of North American and European studies from 2004 to 2019, which incorporates three previously unpublished datasets from eastern Canada, to investigate how mowing intensity impacts the ecology of urban lawns. The meta‐analysis provides aggregated evidence that invertebrate and plant diversity is lower in urban lawns under increased mowing intensity. This decline is independent of the level of contrast between mowing ‘treatment’ and ‘control’ (e.g. height or frequency of mowing), which differed considerably between studies. Intensive mowing also increases the occurrence of pest species (e.g. herbivorous beetle larvae and allergenic plants), though studies in this group were limited to northern environments. Changes in ecosystem‐level variables (soil temperature, soil moisture deficit and carbon deficit) were less evident and suggest changes in abiotic processes may take longer to become apparent. An economic case study of the mowing costs in Trois‐Rivières, Canada, suggests that cost savings of 36% may be possible with a modest reduction of mowing frequency. Synthesis and Applications. Increasing urban biodiversity and reducing greenhouse gas emissions are strong motivators for reducing lawn management intensity. We also suggest that the benefits of reducing pest species while saving lawn management costs may provide additional social and economic incentives for decision makers to review urban greenspace management practices.