Chemotherapy-induced menopause is a well-known condition in breast cancer patients. This menopausal state is usually reversible in younger women and those who had been treated by anthracyclines. Here, we report a 36-year old woman who had a history of previous medullary breast cancer and had received adjuvant CEF regimen after which she developed a contra-lateral medullary breast cancer just following a twin conception. She was in menopausal state after the 3rd cycle of the CEF chemotherapy. Thus, she had given up using contraception. At the 4th year she admitted with abdomen distention. A twin pregnancy was diagnosed by ultrasonography. Ten months later from the birth, a contra-lateral breast cancer was diagnosed. A MRM operation was performed and adjuvant chemotherapy and radiotherapy were administered. She is under follow-up and free of malignancy at the 20th months of the diagnosis. As a conclusion, breast cancer patients and clinicians should be alert on reversible menstrual cycle changes and it is particularly important to assess the endocrine activity after treatment cessation, regularly.