This study was conducted to investigate the combined effect of fatty acid synthase(FASN) and Acetyl CoA Carboxylase-α (ACACA) genes on carcass traits of Korean cattle(Hanwoo). A total of 1,057 commercial Hanwoo cattle provided by the NongHyup Livestock Research Center(NLRC) and Hanwoo Performance Competition(HPC) were used to analyze the effect of four single nucleotide polymorphisms(SNPs) within FASN(g.11280A>G, g.16024A>G, g.16039T>C, and g.17924A>G) and one SNP within ACACA(g.2274G>A) genes. In addition, the effect of genotypic combinations between FASN(g.17924A>G) and ACACA(g.2274G>A) SNPs has been studied with carcass traits. Significant associations were identified between g.17924A>G of FASN and carcass weight and back fat, and between the ACACA gene SNP g.2274G>A and longissimus muscle area with HPC samples. It was also found that both effects of FASN g.17924A>G and ACACA g.2274G>A polymorphisms were consistent in NLRC samples. Combined analyses of both NLRC and HPC samples also revealed the significant associations between the FASN g.17924A>G and carcass weight and back fat and between the ACACA g.2274G>A and back fat, respectively. The effect of the genotypic combination of g.17924A>G within FASN and g.2274G>A within ACACA genes showed that the combination of both GG genotypes of FASN and ACACA SNPs causes higher carcass weight and marbling score. The results of this study indicate that the two SNP markers within the FASN and ACACA genes can be utilized to select superior Hanwoo cows and calves in commercial Hanwoo farms.