Objective: To evaluate prognosis of high-grade endometrial cancers, comparing serous (SC) and clear cell (CCC) types to grade 3 endometrioid carcinoma (ECG3). Methods: Among patients with endometrial cancer treated in two decades, medical records of patients with high-grade endometrial cancer were retrospectively investigated. Results: Of 447 endometrial cancers, 107 (24%) highgrade endometrial cancers were identified, with the increasing incidence in the last decade (28% vs 19%; p = 0.026). There were 24 SC, 14 CCC and 69 ECG3. Median age was 62, 68, and 61 years, respectively, with the CCC type showing an elder age than the ECG3 type (p = 0.012). The rates of patients with Stage IIIc-IV, lymph node assessment or complete resection at primary surgery, and post-operative chemotherapy were not significantly different; however, response rate to first-line chemotherapy in patients with measurable disease was lower in SC than ECG3 (3 / 11, 27% vs 14 / 19, 74%; p = 0.037), regardless of regimens. Five-year overall survival (OS) was 40%, 71%, and 71% respectively, and five-year progression-free survival (PFS) was 25%, 71%, and 61%, respectively, showing SC with worse prognosis than ECG3 on both OS (p = 0.026) and PFS (p = 0.0028). According to the multivariate analysis, age ≥70, Stage IIIc-IV and incomplete resection were independent prognostic factors on poor OS, whereas SC, Stage IIIc- IV and incomplete resection were on poor PFS. Conclusions: The increasing trend of high-grade endometrial cancer and different outcomes according to histological subtypes, especially poor PFS and chemotherapeutic response in SC, were suggested.