Abstract: The relationship between the duration of type 2 diabetes mellitus (T2DM) and the risk of female reproductive malignancies is complex and multifaceted. Large population cohort studies revealed a negative association between the duration of T2DM and the incidence of breast cancer and endometrial cancer. Furthermore, the risk of breast and endometrial cancer is the highest within a short time after T2DM diagnosis and remains remarkably higher in patients with longer diabetes duration than in the nondiabetic population. This phenomenon suggests causal reverse bias and potential detection bias. Nevertheless, T2DM remains an important risk factor for breast and endometrial cancer. Research on the association between diabetes with cervical and ovarian cancer is limited, and results vary by region. Future epidemiological studies should focus on large prospective studies with long follow-up to further investigate this association. Research into the biological mechanisms linking diabetes and female reproductive cancers is also necessary to develop effective cancer prevention and early intervention strategies.