Global longitudinal strain (GLS) is a valuable indicator of subclinical myocardial dysfunction. Whether the effect of aging on subclinical left ventricular dysfunction is sex-specific is not well documented. This study aimed to identify age-related changes in GLS according to sex in patients with a normal left ventricular ejection fraction (LVEF). In this cross-sectional, single-center cohort study in Korea, participants who underwent GLS measurement using 2D speckle-tracking echocardiography were retrospectively reviewed, and participants with normal LVEF (≥ 55%) without documented cardiovascular disease were included. Reduced GLS was defined as absolute values below 18%. Of 682 study participants (mean age, 58; female, 51.5%), 209 (30.6%) had reduced GLS. Females with reduced GLS were older than those with normal GLS (68 vs. 58 years, P < 0.001); with no difference of age in males (55 vs. 57 years; P = 0.265). Univariate analysis showed age to correlate significantly with reduced GLS only in female (r = - 0.364; P < 0.001). In multivariable analysis, female > 66 years old had significantly higher risk of reduced GLS (Odds ratio 2.66; 95% CI 1.22-5.76; P = 0.014). In participants with normal LVEF, GLS decreased with age in females but not in males. Particularly, females aged 66 years and older had a significantly higher risk of reduced GLS. These findings suggest that GLS could be a valuable parameter for assessing subclinical cardiac dysfunction, especially in older females.