Assessment Synchronous primary neoplasms are defined when two or more neoplasms take place concurrently in the same patient. Concomitant endometrial adenocarcinoma and uterine leiomyosarcoma are extremely rare. Here we present an extremely rare case of uterine leiomyosarcoma coexisting with endometrial endometrioid adenocarcinoma of the uterus. A 52 years old woman was reported to a gynecology outpatient clinic with chief complaints lower abdominal pain, severe dysmenorrhea, and irregular vaginal bleeding for 7 months. Ultrasound of pelvis and abdomen showed a solitary intramural fibroid measuring 10x10cm. Surgery was planned and a simple total abdominal hysterectomy with bilateral salpingo-oophorectomy was performed and specimen was sent to the laboratory for examination. Histopathological examination from intramural mass showed high-grade leiomyosarcoma, spindle cell type with less than 50% of myometrial invasion. Sections from thickened endometrium showed endometrial endometrioid adenocarcinoma, FIGO grade I with an invasion of superficial fascicles of myometrium (<50%). Morphological diagnosis was supported by Immunohistochemistry. Here we report an exceptionally rare case of synchronous uterine leiomyosarcoma and endometrial endometrioid adenocarcinoma. Our study may contribute to understand the prognosis of such multiple malignancies, common associations, and etiology of the disease so that a proper plan for further management of the patient can be implemented.