The world's walnuts (Juglans regia L.) production showed rapid growth from less than one million tons to more than three million tons during 1990–2020. The walnut kernel contains a high amount of fats, proteins, and carbohydrates. In this study, the total lipids, proteins, and carbohydrates contents of four commercial walnut cultivars: Alvand, Chaldoran, Caspian, and Persia, together with two promising genotypes: C-25 and 35t, were compared to cv. Chandler in 2019 and 2020. Based on the results, the average percentage of protein in cultivars in two years varied from 15.00% to 19.27%, the percentage of carbohydrates from 17.40% to 29.10%, and the percentage of total lipids from 50.60% to 70.00%. The fatty acids contents showed that the predominant was linoleic acid ranging from 44.60%-63.09%, followed by oleic acid (12.40%-35.02%), linolenic acid (6.64%-14.97%), palmitic acid (7.04%-8.97%) and stearic acid (2.28%-3.63%). Meanwhile, the nut protein (14.90%-19.86%) and carbohydrate (17.40%-29.10%) showed high variability too. The results showed that among the cultivars/genotypes, the highest amount of protein belonged to promising genotype 35t, and the highest amount of total lipid percentage was observed in cv. Persia, and the highest amount of carbohydrates was related to cv. Caspian. The cv. Chandler had the highest linoleic acid content (60.53%), while the cv. Persia had the lowest amount (46.90%). Analysis of regression between fatty acids components showed a close relationship r2 (0.876) between linoleic acid and oleic acid. The analysis of results in two years regarding the total lipids showed that the effect of the year was more than the genotype. Factor analysis using five fatty acids components showed that the first and second factors demonstrated more than 70% of the total variance. The first factor influenced the oleic acid (-0.978) and linoleic acid (0.941) highly. The loading plot of the first and second factors indicated that the change in oleic acid was opposite to linoleic acid, linolenic acid, and stearic acid. In conclusion, walnut cultivars' fatty acids contents showed significant variability, so Chandler, Chaldoran, and 35t were rich in linoleic and linolenic acids. In contrast, others like Persia and C-25 were rich in oleic acid.