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Arsenic (As) is an abundant metalloid in marine environments, while the biogeochemical cycling of As in cold seeps remains poorly understood. We characterized the speciation of As and investigated controls of As distribution in cold seeps of South China Sea. High methane concentrations (0.2-5.5 mmol/L) and rapid sulfate depletion were observed in the seepage. Dissolved inorganic arsenic (DIAs) was enriched in the porewater ranging from 7.5 to 23.5 μg/L. As in the solid phase ranged from 2.9 to 22.6 μg/g, and sulfide mineral-bound As dominated the total arsenic (TAs) pool, followed by iron (manganese, aluminum) oxide-bound As. The significant correlations between porewater Fe 2+ and DIAs reflect the controls of iron on DIAs release. Incubation experiments showed that adsorption to the solid phase and sulfate reduction activity affected the bioavailability and removal of DIAs, suggesting that multiple processes regulate the speciation and transformation of As in seep sediments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)