There is an emerging need for immunotherapeutic modalities that have completely different mechanisms of action from cytotoxic drugs and molecular targeted therapies. This need has been evoked to promote revolutionizing the treatment of cancer. Immunotherapy, including immune checkpoint inhibitors, in gynecological oncology has just begun to be implemented. However, the efficacy of such strategies has been proven. Notably, in the treatment of cervical cancer, vaccine therapy for intraepithelial lesions and immune checkpoint inhibitors for the advanced recurrent disease have been shown to be effective. The efficacy of pembrolizumab monotherapy for the treatment of endometrial cancer in patients with microsatellite instability (MSI)-high and the combination of lenvatinib and pembrolizumab in patients with advanced or recurrent disease has been demonstrated. Pembrolizumab likely will become one of the standard treatments for cervical and endometrial cancers in the future, and indications for this biological may be expanded further in the future. In this chapter, we discuss the current status of evidence and development of immunotherapy, including immune checkpoint inhibitors, in the treatment of cervical, uterine, and ovarian cancers, focusing on Phase III clinical trials.