Twenty individually-housed male Polish Merino lambs with an initial body weight of 25±2 kg were used in the experiment. Each group comprised 5 lambs. Sheep were fed the control or experimental diets enriched in 5% linseed oil (LO), 2 ppm selenium as selenate (SE) or combined addition of 5% LO and 2 ppm selenium (LOSE). The effects of the experimental diets on organs and body weight gain (BWG) of the sheep were small, but the LOSE treatment increased BWG and the weight of M. biceps femoris, M. longissimus dorsi, and the liver. The diets enriched in LO with or without SE decreased the concentration of atherogenic and thrombogenic saturated fatty acids in muscles, liver and perirenal fat tissues. The LO treatment increased the concentration of conjugated linoleic acid (CLA) isomers in the subcutaneous and perirenal fat tissues, liver, M. longissimus dorsi and blood plasma in comparison with the control. Dietary LO with or without SE resulted in negligible changes in the concentration of CLA isomers in M. biceps femoris. The diet enriched in SE decreased the concentration of CLA isomers in both muscles compared with control muscles, whereas it increased in the plasma, liver and perirenal fat tissue. There was a LO and SE interaction for the CLA isomer concentration in the perirenal fat tissue and plasma; this treatment resulted in an increase of the CLA isomer concentration in these tissues compared with the control. The diets enriched in LO or with LO and SE increased the concentration of polyunsaturated fatty acids (PUFA) in the subcutaneous fat tissue, plasma, and perirenal fat tissue. Feeding the diet with LO increased the concentrations of cis9cis12C18:2 and cis9cis12cis15C18:3 in the subcutaneous fat tissue, muscles and plasma in comparison with the control. LO supplementation to sheep increased the concentration of essential (ΣE-AA), non-essential (ΣNE-AA) and sulphur (ΣS-AA) amino acids in the muscles; the diet enriched in LO with or without SE decreased ΣE-AA, ΣNE-AA, ΣS-AA and ΣAA in the liver. These diets increased the nutritional value of meats as the ratio of SFA/MUFA and SFA/PUFA decreased, while the concentration of ΣE-AA increased. The diet containing SE with or without LO resulted in an increase in the Se concentration in meat, plasma, and liver compared with the control.