Tamoxifen (TAM) is widely used in the treatment of breast cancer, and its paradoxical effects on female genital system are well known. During the past 10 years, many descriptions of nonepithelial uterine malignancies related to long-term TAM usage have been reported in the literature. Four uterine sarcoma patients who had history of TAM usage for previous breast cancer are presented in this study. The mean time of exposure to TAM was 6 (range 3-11) years, and the mean cumulative dose of drug was 43.82 g. All patients were postmenopausal, and the mean age was 66 (range 61-73) years at the time of the diagnosis of the uterine malignancy. Two (50%) patients had uterine malignant mixed müllerian tumor, and two (50%) had leiomyosarcoma. In one (25%) patient was diagnosed with endometrial biopsy made for a postmenopausal vaginal bleeding; the others (75%) were asymptomatic and their diseases were diagnosed during the pelvic examination and transvaginal ultrasonography. All patients underwent surgery +/- adjuvant therapy (chemotherapy and/or radiation therapy), and two (50%) patients died because of the sarcoma. In consequence, early detection of TAM-related uterine sarcoma is required for orderly gynecological examination in patients having history of TAM usage for previous breast cancer.