The occurrence of double simultaneous primary cancers is common. However, the occurrence of synchronous primary triple gynecological malignancies is an extremely rare event. In this report, the clinical and pathologic findings of a 56-year-old female patient with synchronous triple primary gynecological cancers including well-differentiated ovarian mucinous cystadenocarcinoma, well-differentiated endometrial endometrioid adenocarcinoma, and uterine leiomyosarcoma were presented. Synchronous primary, well-differentiated endometrial endometrioid adenocarcinoma and leiomyosarcoma of uterus without any ovarian neoplasm has only been once described in the English literature. To our knowledge, the presented patient is the first case in aspect of accompanying ovarian mucinous adenocarcinoma to endometrial endometrioid adenocarcinoma and leiomyosarcoma of uterus.