Mycorrhizal fungi colonize the roots of most terrestrial plants, facilitating mineral nutrient uptake, enhancing stress resistance, and improving soil structure. Although their functional importance is well recognized, they are often overlooked in urban ecological surveys. For instance, of 15685 papers referring to mycorrhizal research published from 1990 to 2014, only 106 papers (0.68%) are related to urban areas. In addition, most of these studies focused only on preliminary assessment of mycorrhizal fungal diversity and community structure; knowledge of how these fungi are affected by urbanization and the roles they play in urban ecosystems remains relatively rare. However, mycorrhizal fungi are sensitive to various biotic and abiotic factors, and it is well documented that urbanization usually reduces their abundance and species richness, and changes their community composition. Thus, mycorrhizal fungi, especially ectomycorrhizal fungi, have potential as bioindicators of the quality of urban green-space systems. Anthropogenic activities cause many local environmental problems such as biotic homogenization, soil degradation, and pollution. Coupled with human management of landscapes, a variety of properties of urban environments are identified that may affect the survival of mycorrhizal fungi. However, given the ecological complexity of urban ecosystems, their mechanisms of action are still largely unknown. This paper first reviews the changes in mycorrhizal fungal diversity in cities, and then highlights the ecological processes and factors that may potentially affect their persistence. The subsequent discussion focuses on potential ecological benefits from mycorrhizal mutualisms. Because of its positive effect on plant nutrition and soil structure, the application of mycorrhizal technology in damaged ecosystems has been advocated. Nevertheless, because clear and comprehensive findings from field research are lacking, this technology is not available for landscape management, a field beset with many uncertainties and assumptions. Despite its promise, little work has been done on this technology, and more research is needed in the future to develop practical approaches within the context of urban landscapes. In general, knowledge of mycorrhizal fungi in cities is somewhat limited, and it is often hindered by the complexity of urban environments. A more sophisticated, systematic, and standard framework of research is needed to assess the diversity of mycorrhizal fungi in urban habitats and to clarify the impact of urbanization on their distribution and assemblages, as well as to understand the broader implications of altered fungal communities. This is of great importance in microbial resource conservation and green-space maintenance in cities.