To analyze prognostic factors and survival outcomes in patients with synchronous endometrial and ovarian cancer (SEOC) to guide clinical management. We conducted a retrospective cohort study of patients diagnosed with SEOC at Peking University People's Hospital between January 2004 and December 2024. Clinicopathological data were collected, and oncological outcomes, including progression-free survival (PFS) and overall survival (OS), were analyzed along with their associated prognostic factors. Among 64 included patients, vaginal bleeding was the predominant presenting symptom. Thirty-six patients were diagnosed with concordant endometrioid carcinoma, which was the most common histological type. All patients underwent surgical treatment, among whom 56 received platinum-based chemotherapy postoperatively, with a platinum sensitivity rate of 67.9%. The median PFS and OS were 27 months (range 3-215) and 41 months (range 7-246), respectively. On multivariate analysis, advanced FIGO stage of ovarian cancer (HR = 2.764; 95% CI 1.169-6.536, P = 0.021) independently predicted worse PFS, while platinum resistance (HR = 6.962; 95% CI 2.052-23.619, P = 0.002) was significantly associated with reduced OS. In this cohort, platinum sensitivity was observed in 67.9% of cases. The advanced ovarian FIGO stage and platinum resistance independently correlated with inferior survival, underscoring the urgent need for tailored therapeutic strategies and intensified surveillance in platinum-resistant SEOC.