Objective: Pregnancy and childbirth are stressful conditions for females. Insulin resistance increases during pregnancy as a result of various factors. This study aimed to assess insulin resistance according to maternal age at childbirth. Methods: The data used in this study were obtained from the Korean National Health and Nutrition Examination Survey (KNHANES) conducted by the Korean Ministry of Health and Welfare in 2010. This study included a total of 2,233 non-diabetic females aged ≥ 30 years. Subjects were subdivided depending on their age at their first and last childbirth. Homeostasis model assessment of insulin resistance (HOMA-IR) was then performed in individuals from different age groups and obesity statuses. Results: The age at first childbirth showed a negative relationship with HOMA-IR, both before and after adjustment for non-obese and non-abdominally obese females. After adjusting for age, lifestyle, and reproductive factors, the age at last childbirth had a positive relationship with HOMA-IR in non-obese and non-abdominally obese females. In multivariate logistic regression analysis, the age at first and last childbirth were significantly associated with highest quartile of HOMA-IR. The OR was 0.9 [95% CI 0.83~0.99] according to age at first childbirth, and 1.09 [95% CI 1.02~1.16] according to age at last childbirth in non-obese females. Conclusion: In conclusion, our study suggests that insulin resistance is increased in females who experienced their first childbirth at a young age or last childbirth at a later age, particularly in non-obese individuals. Because these data suggest that childbearing age could be an independent risk factor for diabetes, a high-quality prospective study assessing childbearing age and insulin resistance should be performed.