Castleman's disease (CD) is a rare benign disorder of unknown etiology characterized by proliferation of lymphoid tissues. Seventy percent of this tumor occurs in the mediastinum and it is seldom found in neck, pancreas or pelvis. We report a case of asymptomatic pelvic CD initially presenting as an adnexal tumor in a 27-year-old woman. Initial transvaginal sonography revealed 7-cm-sized hyperechoic mass adjacent to the right ovary and the following abdominal computed tomography scanning showed the same sized mass located on the right extraperitoneal pelvic cavity. Laparoscopic mass excision was performed without any complication and pathological diagnosis was made as CD. CD should be included in the differential diagnosis of female pelvic masses which are noted in the pelvic cavity. In this report, we review the clinicopathological findings in a presentation of CD.