Lynch syndrome is a genetic malignancy syndrome affecting the colon, endometrium, and other organs. It is difficult to find a Lynch syndrome patient without any family history of cancer. We have recently examined an endometrial cancer patient with a MSH2 gene mutation without a family history of cancer. A 55-year old Korean woman was admitted to a local clinic for vaginal bleeding. An endometrial biopsy revealed the presence of adenocarcinoma (endometrioid type, grade 1). After surgical staging, no further adjuvant therapy was required. Analysis of the tissue using immunohistochemistry (IHC) showed the endometrium stained negatively for MSH2. Microsatellite instability (MSI) was analyzed for five markers. The patient was scored as unstable. Further, additional gene sequencing revealed one missense mutation in c.23C > T (p.Thr8Met). This is the first case of Lynch syndrome endometrial cancer in Korea in which the patient does not have any family history of cancer.