Objectives: The age of menopause is affected by several factors. In this study we aimed to identify the age of natural menopause and its related factors in a large-scale population-based cohort in Iran. Methods: In this study, a subset of data collected during the enrollment phase of the Tabari cohort study was utilized. Reproductive history and other related data were collected using a structured questionnaire. Blood samples were obtained from all participants. Data were analyzed using chi-square test, independent t test, and ANOVA as well as a multivariate linear regression model. Results: Among participants of the Tabari cohort, 2,753 were menopausal women. The mean age of natural and induced menopause was 49.2 ± 4.7 and 43.2 ± 6.4 years, respectively (P = 0.001). The number of pregnancies, duration of breastfeeding, level of education, residency, presence of thyroid disease, and body mass index affected the age of menopause. After adjustments for confounding variables, the number of pregnancies remained significantly associated with late menopause. Conclusions The age of natural menopause in this study was similar to that in other studies, and the number of pregnancies was positively associated with the age of menopause after adjustments for confounding variables.