A lack of estrogen due to menopause changes metabolic homeostasis, which increases the risk of metabolic syndrome (MetS) in postmenopausal women. Hormone therapy (HT) has beneficial effects on chronic diseases as well as on menopause symptoms. The aim of this study was to investigate the association of HT use with MetS and its components by diabetes status in middle-aged postmenopausal Korean women. A cross-sectional analysis was undertaken of a total of 39,295 non-diabetic and 3,359 diabetic postmenopausal women aged 40 to 69 years from the Health Examinees-Gem (HEXA-G) study (2004–2013). The mean differences in the MetS components by HT use were assessed using a general linear model and Tukey’s multiple comparisons tests. The prevalence odds ratio (POR) and 95% confidence intervals (CIs) were estimated using the logistic regression model. HT use was associated with lower fasting glucose level, total cholesterol, systolic blood pressure, body mass index, waist circumference, and waist-to-hip ratio among both diabetic and non-diabetic women. In non-diabetic women, HT ‘ever’ use was negatively associated with the prevalence of MetS (POR = 0.80, 95% CI: 0.75-0.85), and current users had a lower prevalence of MetS (POR = 0.68, 95% CI: 0.60-0.76). A longer duration of HT use was associated with a decreasing prevalence of MetS. We did not find heterogeneity by age regarding MetS prevalence. Our results suggest that HT use is negatively associated with the prevalence of MetS among postmenopausal women. However, further longitudinal studies are required to investigate the effect of HT on MetS in Korean women.