Objective: Lynch syndrome, as known as hereditary non-polyposis colorectal cancer, is an autosomal dominant inherited disease by germline mutations in DNA repair genes including MLH1, MSH2, MSH6, PMS2 and EPCAM. In Lynch syndrome, endometrial cancer is the second most common cancer. High microsatellite instability and mismatch repair deficiency, which are characteristic of lynch syndrome, are one of the molecular-based classification of endometrial cancer. Endometrial cancer with lynch syndrome has become more important with the advent of FDA-approved Pembrolizumab in these traits. However, the national prevalence of germline mutation in DNA repair genes in Korean women with Lynch syndrome remains unknown. The aim of the study is to find most common mutation of DNA repair genes in Korean women with Lynch syndrome-associated endometrial carcinoma. Methods: Ten reports of Korean endometrial cancer patients who confirmed lynch syndrome and three patients who were detected at Chung-Ang University Hospital were reviewed. Age, the family history based on Amsterdam criteria II, immunohistochemical analysis, germline mutation, microsatellite instability status, FIGO stage, grade, and type were collected. Descriptive statistical analysis was used. Results: A total 28 cases were summarized. Eighteen (64.3%) cases met Amsterdam criteria II for Lynch syndrome. Mean age at onset of endometrial cancer was 49.0 years (range 27-60 years). Immunohistochemical analysis was reported in 20 patients and losses of MLH1, MSH2, MSH6, or PMS2 proteins were observed in endometrial cancer tissues. The germline mutations of MLH1, MSH2 and MSH6 were found in 15 (53.6%), 9 (32.1%) and 4 (14.3%), respectively. Microsatellite instability was assessed in ten patients and nine patients had high microsatellite instability. Conclusion: MLH1 is most common germline mutation and its mutations were located in ten sites which could be novel in Korean women with Lynch syndrome-associated endometrial carcinoma.