Objectives: This study compares the clinical and pathological characteristics as well as prognosis among patients who are diagnosed of epithelial ovarian carcinoma arising from endometriosis (EOOC) and are just concomitantly with endometriosis (ECOC). Methods: A retrospective review, simultaneously from January 1995 to December 2014 at OB/GYN Hospital of Fudan University, involved patients diagnosed with epithelial ovarian cancer (EOC) and endometriosis, was performed. Firstly, the patients were divided into EOOC and ECOC according to whether there was a pathological continuity between EOC lesion and endometriosis or not. Then collect the clinical characteristics and pathological features of individual cases. And use logistic regression analysis to define the risk factors for EOOC. Finally, use the Kaplain-Meier method to compare the differences in overall survival and disease-free survival among groups. Results: The retrospective review identified 149 patients as EOC with endometriosis, and the result showed that there were 110 cases (73.8%) diagnosed with EOOC and 39 with ECOC. Compared with ECOC group, more patients with EOOC were at FIGO stage I (P<0.01) and took with clear cell carcinoma (P<0.01). The number of patients with ECOC that were diagnosed with FIGO stage II (P<0.01) or III (P<0.05) and high-grade serous adenocarcinoma (P<0.01) was larger. Logistic regression analysis showed that FIGO stage and tumor cell type were related risk factors for EOOC diagnosis. No significant difference in 5-year overall survival or disease-free survival was found among groups. Conclusions: Patients with EOOC or ECOC had a similar prognosis indicated by survival rates and carried with different FIGO stages and tumor histological types.