The adsorption and oxidation of arsenite [As(III)] by soil components are critical processes that influence its toxicity and mobility. However, the specific mechanisms driving the synergistic interactions among bacteria, soil minerals, and humic acid (HA) in these processes remain insufficiently understood. This study investigated the effects of goethite and HA association on As(III) adsorption-oxidation by the As(III)-oxidizing bacterium SY8 using batch incubation experiments and spectroscopic analyses. The results indicated that goethite inhibited the growth of SY8, but its binary and ternary composites with HA and SY8 substantially enhanced the adsorption and oxidation of As(III) compared to SY8 alone. This enhancement could be attributed to the generation of hydroxyl radicals (·OH) through Fenton-like reactions that contribute to the enhanced oxidation of As(III). The Fenton-like reactions involved interactions between H