To evaluate the feasibility of ovarian preservation at the time of operation in patients with clinical stage I endometrial carcinoma. The data of 499 consecutive patients with clinical stage 1 endometrial cancer operated between January 2001 and December 2011 were retrospectively reviewed. Clinical and pathologic information and the intraoperative inspection findings of ovaries were evaluated to find the factors associated with the coexisting ovarian malignancy. The mean age of patients was 56.8 ± 9.8 years. Coexisting ovarian tumors were detected in 38 patients (7.6 %), and 28 (5.6 %) of them were malignant (12 metastatic and 16 synchronous primaries). Most of the patients were postmenopausal (n = 371, 74.3 %) and 60 (12 %) of the patients were at the age of 45 years or less. Coexisting malignancy was detected in 9 % (n = 11) of the premenopausal patients and in 5 % (n = 3) of the patients aged 45 years or less. Multivariate analysis revealed that serosal invasion, tubal involvement, and positive abdominal cytology were independent risk factors for coexisting ovarian malignancy. The sensitivity, specificity, positive predictive value and negative predictive value of the intraoperative examination for the diagnosis of benign/normal ovary was 99.6, 78.8, 98.5 and 92.9 %, respectively. The incidence of coexisting ovarian malignancy in clinical stage I endometrial carcinoma is low. Although occult metastasis cannot be excluded at all, careful intraoperative inspection of ovaries seems valuable for the prediction of co-existing ovarian malignancy.