Permafrost thaw and coastal erosion are key drivers of mercury (Hg) release from Arctic coastal regions. This mobilization eventually poses risks to marine ecosystems, as Hg can be transformed into methylmercury (MeHg), a potent and bioaccumulating neurotoxin. Understanding the Hg dynamics in coastal zones is essential to assess their role in the pan-Arctic Hg cycle under the One Health approach. In this study, we quantified terrestrial Hg stocks of the Yukon coast in northwestern Canada, estimated the annual Hg release through coastal erosion, and investigated the fate of Hg in the marine environment of the Beaufort Sea. We measured total Hg and MeHg concentrations in terrestrial and marine sediment samples and filled data gaps using a random forest model. We quantified Hg stocks and fluxes by considering cliff height, ground ice content and regional erosion rates. The total Hg stock of the Yukon coast (approximately 300 km long, extending 2 km inland) is estimated at 381,080 (271,540–501,930) kg, of which 113 (87–163) kg are released annually through coastal erosion. MeHg concentrations, measured here for the first time, were higher in terrestrial sediments (0.29 ± 0.25 µg kg-1) compared to marine sediments (0.21 ± 0.08 µg kg-1). The same pattern was observed for Hg concentrations in the nearshore zone (up to 2000 m distance from shore). This suggests that some Hg released from coastal erosion is not directly buried in marine sediments but remains in the water column, probably settling in sediments beyond the shelf break of the Beaufort Sea, where higher Hg concentrations have been observed before. Other pathways include exchange with the atmosphere, transformations within the water column (including methylation), and uptake of MeHg by phytoplankton, thereby entering the food web. Our results indicate no immediate risks to local communities or ecosystems. However, as permafrost thaw and coastal erosion intensify with ongoing Arctic warming, monitoring of fish and marine mammals might become increasingly important to detect potential long-term bioaccumulation and ecosystem impacts.