The impact of arsenic (As) discharge related to a past mining activity in the Bravona River and its tributary, the Presa River, was investigated in an edible fish, the brown trout (Salmo trutta). Fish was sampled in four stations along a contamination gradient. Arsenic was measured in five organs type (operculum, gills, liver, muscle, and axial skeleton). Almost 70 years after the suspension of the mining activity, As levels in water remain high. The results indicated a strong As contamination in fish collected downstream from the mine. The operculum, liver, and gills showed the highest As concentrations whereas levels in muscle were lower. A strong positive correlation between As concentrations in water and in tissues was observed. Bioaccumulation occurred preferentially in the gills, operculum, and liver. Since As levels in tissues of S. trutta followed the pollution gradient, this species appears useful as biomonitor for metalloid accumulation.