Antimony (Sb) and arsenic (As) are metalloid contaminants often associated with mining and smelting. Both elements are widely dispersed in contaminated environments, but the ecological risk posed by Sb is much less understood. The aim of this study was to understand accumulation and biotransfer of both metalloids in aquatic foodwebs of the Macleay River catchment of northern NSW, a catchment strongly affected by Sb and As contamination by over a century of gold (Au)-Sb mining and processing. Metalloids were quantified in the water, sediment, and biota representing various trophic levels and diverse species assemblages at fifteen morphologically and hydrologically different sites. All stream components were enriched with the metalloids close to the source (e.g. 8 – 1200 µg g-1 Sb and 13 – 255 µg g-1 As in stream autotrophs) but this enrichment decreased substantially downstream. The spatial distribution of Sb in water and sediment was strongly associated with distance from the mine, unlike As, which was independent of distance. While bioaccumulation was evident in the food webs, and some of the highest Sb concentrations ever detected in biota were recorded, As showed much greater uptake efficiency and a different distribution to Sb in biota tissues. Temporal changes in metalloid sources (water, detritus, and sediment) had little effect on Sb and As bioaccumulation in trophic groups. Neither Sb nor As showed evidence of biomagnification through the food webs of the different sites. Rather, there was biodiminution of both metalloids with increasing trophic level. This study provides new insight into metalloid flux and burdens in contaminated aquatic food webs, and information essential for protective risk management in rehabilitation strategies.