Because many livestock with avian influenza and foot and mouth disease have been disposed of at landfills, underground water contamination is a big problem for people living near these landfills as well as burial sites. Biological oxygen demand (BOD), NH4, total dissolved solids (TDS), chloride and potassium have been used as markers of contamination from the leachates of animal carcasses. However, livestock manure and vegetable oils from compost are also a source of these markers. In this study, we propose arachidonic acid (C20:4) as a specific indicator of leachates from animal carcasses, and the presence of arachidonic acid in underground water is suggested to be a potential marker of contamination from the leachates of animal carcasses. Based on the specific fatty acid composition, the fatty acid profiles of the carcass leachates, livestock manure and vegetable oil were examined, and multidimensional scaling (MDS) analyses of the fatty acids showed pronounced differences between the carcass leachates, livestock manure and vegetable oils in this study. MDS analyses of fatty acids can also be used as a potential indicator of contamination from the leachates of animal carcasses in groundwater.