The objective of the study was to investigate the effects of sex and slaughter age on the fatty acid (FA) composition and stearoyl-CoA desaturase gene expression in muscle and adipose tissue. Twenty-four Charolais x Simmental crossbred bulls and heifers were raised under similar conditions and slaughtered at 14 or 18 months of age. The total amount of FA in muscle increased markedly in older animals with higher contents of monounsaturated FA (MUFA) in heifers than bulls. The proportions of MUFA and desaturation indices were higher in heifers, whereas polyunsaturated FA were higher in bulls in both muscle and subcutaneous adipose tissue. The results of this study demonstrated sex-dependent differences in the FA composition of muscle and subcutaneous adipose tissue from cattle slaughtered at different ages. The expression of the stearoyl-CoA desaturase gene was higher in the adipose tissue of heifers compared to bulls.