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 C-cycling). 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. Biological traits analysis was used to quantify the potential contribution of taxa towards the delivery of selected ecosystem functions. Ten morphological, life history and behavioural traits were selected that influenced fundamental mudflat functions mediated by macrofauna. For example, organisms with small body sizes and short life spans may facilitate organic C-cycling, whilst taxa that dwell near the sediment surface are most likely to be consumed by predators. Each of the 10 traits were represented by 3 to 5 subcategories, or modalities; e.g. feeding mode was subdivided into deposit feeder, suspension and filter feeder, predator and/or scavenger, and grazer. The affinity of each taxon to a trait modality was coded using a ‘fuzzy coding’ procedure. The score assigned to each modality (e.g. 0 = species had no affinity to that modality, 1.0 = complete affinity) was such that the scores for a trait summed to 1. When the affinity of a taxon for a modality was unknown, higher taxon level information (e.g. genus < order < class) were used. 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 de com position 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.