Background: Breast cancer survivors have slightly increased risk of second primary cancers. Importance of screening for second cancers has been raised due to increased survival in those populations. Not only having genetic risk such as BRCA mutation, but also treatment-related risk presents. The most common second primary cancer is breast cancer. Colon cancer, uterine cancer, and ovarian cancer showed increased cumulative incidence. In this study, we assessed development second primary cancers in breast cancer survivors. Methods: Medical record of breast cancer patients was reviewed retrospectively in three tertiary medical institutions. Available data of ICD-9 record after breast cancer diagnosis was evaluated. Diagnosis of second primary breast cancer was excluded in evaluation. Results: Since Jan 1989 to Jan 2014, available medical records were reviewed in breast cancer patients(N = 5880) in three institutions(one urban and the other two rural institutions). Cumulative incidence of overall second primary cancers was 4.57%. Among 269 second primary cancers, thyroid cancer(44.2%) was most common second primary cancer, followed by gastric cancer(10.0%). Gastric cancers were more common in rural institution than urban area(14.2 % vs 5.5%), while incidence of thyroid cancer is elevated in urban institution(57.8% vs 31.9%). Among 9 patients who has been diagnosed endometrial cancer, 7 patients had history of selective estrogen receptor modulator(tamoxifen or toremifen) treatment. Development of lung cancer was not related to breast cancer radiation treatment(4 of 15 patients). Leukemia after breast cancer treatment was diagnosed in 5 patients (8.5% of second primary cancers), three of them were adult T cell leukemia and two of them were acute myeloid leukemia. Conclusions: Incidence of cancer in general population was reflected to development of second primary cancer in breast cancer survivors. Endocrine treatment was related increased incidence of endometrial cancer, respectively. Application of personalized cancer screening plan would be important in this patient group.