The coast of Croatia, bordering the Adriatic Sea, is heavily polluted with metals, including mercury, from oil refineries, thermal power plants, energy conversion plants, natural gas production and processing plants, the petrochemical and cement industries as well as fertilizer production. For example, on the north-eastern coast of the Adriatic Sea, an estimated 56 tons of mercury were released into the sea by a chloralkali plant over its 41 years of activity. Elevated mercury concentrations in sediments and the bioaccumulation of methylmercury in marine organisms have been found in this area: 41% of the captive Atlantic Bluefin tuna farmed in the Adriatic Sea contained mercury above the level considered safe under EU and Croatian legislation. A case study was undertaken on selected sites in Croatia, bordering the Adriatic Sea, to test hair and blood samples of the Croatian population for mercury levels. The frequency of consumption of certain fish species showed a significant positive association with the measured mercury levels. While fish consumption is a source of valuable nutrients, such as omega-3 fatty acids, folic acid and selenium, it can also be the source of methylmercury. Consequently, intersectoral efforts to inform local communities (especially pregnant women) regarding local fish consumption and some of the pollution issues, and continuous monitoring of fish and people in the affected area will help to tackle SDG 3.9 (reduce the number of deaths and illnesses from hazardous chemicals) and SDG 14.1 (prevent and significantly reduce marine pollution, in particular from land-based activities). Further studies should be undertaken, including human biomonitoring, in a wider population, with a specific focus on areas where environmental pollution and higher exposure have been identified.