Signet ring cell carcinoma (SRCC) of the ovary is most commonly metastatic from a primary lesions. Primary ovarian SRCC is a rare and the distinction between primary and metastatic SRCC of the ovary may be difficult. We herein present a case of primary SRCC of the ovary in a 45 years women presenting with right ovarian mass sized 18 x 16 x 11cm. Total abdominal hysterectomy with bilateral salpingo – oophorectomy, partial omentectomy were performed. Upon histological examination, mucinous carcinoma composed predominantly of signet ring cells was observed in the right ovary. The results of immunohistochemistry examination included diffuse positivity for cytokeratin, Endothelial Membrane Antigen(EMA), Desmin,but tumor was negative for estrogen receptor, progesterone receptor, CD117, synaptophysin and chromogenin. A preoperative computed tomography (CT) scan of the abdomen and a postoperative positron emission tomography – CT scan did not reveal any suspicious extraovarian lesions. Basedon the histological and clinicoradiological examinations, this case was diagnosed as a primary ovarian SRCC.