This study was performed to determine the genotype and allele frequencies and the association between the leptin gene Sau3AI polymorphism and some performance traits in Simmental (n=60) and Brown Swiss (n=62) cattle in the province of Erzurum, Türkiye. Considering the allele frequencies in the population, the frequency of the A allele was 0.87 and the frequency of the B allele was 0.13 in Simmental cattle, and the frequency of the A allele was 0.94 and the frequency of the B allele was 0.06 in Brown Swiss cattle. According to the analysis conducted in the Simmental breed, the general averages were found to be 5422.4 ± 1901.74 kg for actual milk yield, 5626.6 ± 1475.85 kg for 305-day milk yield, 298.7 ± 84.80 days for lactation duration, and 18.5 ± 4.84 kg for daily milk yield. As a result of the analysis in the Brown Swiss breed, the general averages were 3917.8 ± 1584.38 kg for actual milk yield, 4614.3 ± 982.62 kg for 305-day milk yield, 254.9 ± 99.88 days for lactation duration, and 16.0 ± 3.82 kg for daily milk yield. According to the statistical analysis results, the impact of genotype on milk yield traits was insignificant in Simmental and Brown Swiss cattle.