The aim of this study was to investigate the effects of supplementation of diets containing rapeseed (R-O) and fish (F-O) oils with carnosic acid (C-A) and Se (as Se-enriched yeast (Se-Y) or selenate (Se-VI)) on concentrations of fatty acids (FAs), tocopherols, cholesterol and malondialdehyde (MDA) in lamb kidneys. Male Corriedale lambs with average body weight (23.3 ± 2.1 kg) and age (82–90 days) were individually penned, and divided into 4 groups, 6 animals each. After the 3-week preliminary period, the 35-day dietary experiment was conducted with the following experimental design: 1) control diet – basal diet (BD) with 2% R-O and 1% F-O; 2) CA diet – BD with 2% R-O, 1% F-O and 0.1% C-A; 3) CA-SeY diet – BD with 2% R-O, 1% F-O, 0.1% C-A and 0.35 mg Se (as Se-Y)/kg BD; and 4) CA-SeVI diet – BD with 2% R-O, 1% F-O, 0.1% C-A and 0.35 mg Se (as Se-VI)/kg BD. Feeding lambs with the CA-SeVI diet increased (P ≤ 0.05) the live weight, kidneys weight and feed conversion efficiency when compared to lambs fed CA and CA-SeY diets. The CA-SeY diet decreased (P ≤ 0.05) the concentration of the sum of FAs in the kidneys compared to the control and CA-SeVI diets. The experimental diets reduced (P ≤ 0.05) the level of n-3 polyunsaturated FAs (PUFAs), long-chain PUFAs (LPUFAs) and the hypocholesterolemic/ hypercholesterolemic FAs ratio compared to the control diet. The experimental diets enriched with Se-Y or Se-VI reduced (P ≤ 0.05) the concentration of MDA in the kidneys compared to the control and CA diets. The experimental diet containing only C-A stimulated (P ≤ 0.05) the oxidative degradation of PUFAs as compared to the control and other experimental diets. The modified atherogenic index was used to evaluate atherogenic properties in the kidneys. The obtained results help to understand the potential beneficial impact of C-A, Se-Y and Se-VI supplements in diets with F-O (rich in LPUFAs) on the lipid content and oxidative parameters in lamb kidneys. The investigation provides also new practical knowledge for nutritionists carrying out further studies aimed at improving farm animal health, growth performance and welfare of lambs.