Seed oil contents, fatty acid compositions and mineral contents of twenty Onobrychis viciifolia genotypes (sainfoin) were investigated in this study. The fatty acid composition of O. viciifolia genotypes had different saturated and unsaturated fatty acids. For saturated fatty acids, O. viciifolia genotypes contained palmitic and stearic acids as the major component and contained small amount of myristic and arachidic acids. The major unsaturated fatty acids were identified as oleic, linoleic and linolenic acids. Total saturated fatty acids contents varied between 10.50 and 14.28% and total unsaturated fatty acid contents varied between 85.72 and 89.50%. Co, Mn, Fe, Cu, Ni and Zn were detected in crop seeds in different amounts. The proximate analysis indicated that seed Co contents varied between 13.53 and 114.83 ppm, Mn contents between 28.14 and 97.20 ppm, Fe contents between 113.7 and 277.7 ppm, Cu contents between 7.19 and 12.24 ppm, Ni contents between 1.14 and 19.73 ppm and Zn contents between 26.03 and 52.39 ppm, respectively. The result of this study suggest that further studies are obligatory to invigorate in terms of animal nutrition and phytochemicals of O. viciifolia.