Though often seen as degraded and lifeless, urban soils are dynamic ecosystems inhabited by diverse, functionally important organisms that provide many ecosystem services. In urbanized landscapes, human activities influence spatiotemporal heterogeneity of soil biodiversity. Historically, urban soil biodiversity research focused on population sizes and dynamics and community structure patterns. To guide future advances, we propose a multidimensional conceptual framework emphasizing that urban soils are complex social-ecological systems in which abiotic properties, organisms, and social systems have feedback relationships that give rise to dynamic spatiotemporal patterns of communities and ecosystem services. With this view, urban soil biodiversity needs to be examined across scales, from local patches through neighborhood and regional mosaics, with consideration of historical legacies and short-through-long-term environmental and social drivers. Improved understanding of urban social-ecological soil systems can provide actionable knowledge to inform planning, policies, and management for conservation and restoration of urban soils and their ecosystem services. To support decision-making, education and communication efforts are essential for raising society’s awareness and appreciation for soil organisms and healthy urban soils. We advocate prioritizing urban soil biodiversity more widely in research, teaching, policies, and environmental management to support the future sustainability of urban systems and human well-being.