For ovarian cancer (OC) patients with advanced or metastatic disease, standard treatments (chemotherapy and radiotherapy) are not very effective and have undesirable side effects. Newer and more promising approaches in cancer treatment use components of the immune system. In this study, we applied an adoptive immunotherapy-based approach using a cancer testis antigen, sperm protein 17, as a target for the treatment of human metastatic OC in a NOD.CB17-PrkDCcid/J (nonobese, diabetic severe combined immunodeficient) mouse model. We used the human SK-OV-3A2.A3 OC cell line, endogenously expressing sperm protein 17, to induce tumor growth in mice. We provide direct evidence, for the first time, that in vitro cultured, monoclonal, cytotoxic T lymphocytes (derived either from advanced OC patients or from healthy donors), specific for sperm protein 17, can eradicate human metastatic OC cells. In addition, we observed no evidence of autoimmunity after histologic examination of the tissue sections adding to the safety profile of our approach.