Primary natural killer (NK)/T cell lymphoma of the uterus is extremely rare. A case of primary NK/T cell lymphoma arising from the endometrium of the uterus was diagnosed by curettage which demonstrated the typical pathological characteristics of NK/T cell lymphoma. The patient received induction chemotherapy but refused hysterectomy. Later she developed bone marrow infiltration and eventually died on day 76 after diagnosis. The natural course of primary endometrial (NK)/T cell lymphoma was very aggressive. Conventional cytotoxic chemotherapy may be ineffective for this aggressive disease.