This work reports the first integrated mercury study in an Antarctic ecosystem. Sample collection took place in Deception Island, an active volcano in the South Shetland Islands, in several environmental compartments (water, snow, sediments and vegetation) and different locations, during December 2011. The results suggest that volcanic activity is the most important Hg source. Mercury levels in water and sediments sampled at two fumaroles were up to 10,000 times higher than in the other sampling sites. Dissolved methylmercury (MeHg) is below the detection limit in those samples, probably due to the very high temperature found in fumaroles (above 80°C). On the other hand MeHg accounted for, on average, 23% of total dissolved Hg in the saline waters of Foster bay, which suggests exceptional conditions for Hg methylation. Combined with the high residence time of the water in Foster bay, the results point to the existence of a MeHg pool available for aquatic living organisms.