Mudflats—unvegetated, soft-sediment, intertidal habitats—support macrofaunal assemblages that contribute to a number of important ecosystem functions (e.g. food for fish and birds, nutrient and Ccycling). These habitats are widespread but are threatened by increasing pressure from anthropogenic activities. Greater knowledge of the consequences of biodiversity loss for the functioning of ecosystems can aid management, by identifying potential threats. Systematic searches of the Web of Science and SCOPUS identified 163 published datasets of essentially ‘pristine’ mudflat macrofaunal assemblages, comprising data on 448 taxa from 4 climatic zones and 10 biogeographic regions. Broad-scale patterns of trait distribution confirmed established patterns showing that taxa at low latitudes have smaller body sizes, shorter life spans and more taxa have exoskeletons, and that direct developmental modes are more prevalent at high latitudes. Greater occurrences of burrow dwellers in the temperate zone may support greater rates of sediment turnover, organic matter decomposition and nutrient cycling, whereas in the tropics, tube dwellers provide more biogenic habitat. Despite these trait differences, the overall similarity in trait composition relative to taxonomic composition indicated that globally, mudflats are functionally similar. The functional redundancy observed across regional and climatic boundaries suggests that ecosystem functioning and service delivery will show some resilience in the face of perturbation. However, the growing anthropogenic pressures on coastal mudflats means the risk of system collapse, beyond resilience thresholds, is high. This study illustrates how an extensive body of published literature can provide a foundation for developing a global understanding of ecological functioning in mudflats to inform management responses.