Many cancer patients become infertile after treatment with anticancer drugs or radiotherapy. To restore fertility, cryopreservation of sperm, ova/fertilized ova, or ovarian tissue is considered as one of the available options; however, this method gives very low pregnancy rate due to cellular injury caused by freezing. Since it is impossible to collect sperm or ova prior to sexual maturity, there is no other treatment approach that can be applied in the case of children with cancer. In this paper, we propose anew transplantation procedure using rat models in which the function of the reproductive organs is preserved by temporarily transplanting them between living donors and recipients, without the requirement for cryopreservation of the ovarian tissue. These procedures are based on the plasticsurgery techniques that are aimed at restoration of amputated limbs. We removed the ovary from a recipient rat, temporarily transplanted it into a recipient rat, and finally retransplantated into the donor; this subsequently resulted in a successful natural pregnancy and delivery. Microscopic observation revealed that most ova that were transplanted to the ovary by vascular anastomosis survived. In addition, femoral bone mineral density analysis confirmed increased bone density compared with that measured prior to the ovarian transplantation. Furthermore, since mammals possess a pair of ovaries, the procedure developed in this study can also be applied to fields other than medicine. For example, the reproductive efficiency of animals after menopause can be increased through reproductive organ transplantation, which can be achieved by preservation of one of these ovaries for transplantation.