Early menarche is known to be associated with diabetes, however this association remains controversial. Our study aimed to investigate the possible association between age at menarche and diabetes prevalence in post-menopausal Korean women. This study included 3,254 post-menopausal Korean women aged 50-85 years from the Korea National Health and Nutrition Examination Survey IV (KNHANES 2007-2009). Logistic regression analyses were used to estimate odds ratios (ORs) for diabetes prevalence. Levels of biochemical markers were compared according to groups by age at menarche. Women in the earlier menarche age group (10-12 years) showed higher levels of fasting blood glucose (FBG) and scores of homeostatic model assessment in the insulin resistance (HOMA-IR) index than other groups (p <0.05). After adjusting for potential confounding factors, early age at menarche was significantly associated with a higher prevalence of diabetes (OR 1.86, 95% confidence intervals [CI] 1.07-3.23). The observed association remained significant despite additional adjustment for body mass index and waist circumference (OR 1.82, 95% CI 1.03-3.23) and despite further adjustments for FBG levels and HOMA-IR index (OR 2.25, 95% CI 1.11-4.55). Our findings strengthen the hypothesis that younger age at menarche is associated with increased diabetes prevalence in the Korean population.