Background: The ovarian function restoration of premature ovarian insufficiency (POI) patients is one of the most challenging problems in the reproduction field, as no evidence-based efficient therapy exists. Regenerative medicine with peripheral blood mononuclear cells (PBMCs) transplantation sheds light on this issue. However, the efficiency and safety of PBMCs treatment in patients with natural ovarian aging (NOA) remain unclear.Methods: To investigate the effect of PBMCs alone or combined with PRP on NOA functional recovery, we used 13-month-old female Sprague–Dawley (SD) rats as an NOA model. Seventy-two NOA rats were randomly divided into three groups: the NOA control group, PBMCs group, and PBMCs combined with platelet-rich plasma (PRP) group. PBMCs and PRP were transplanted by intraovarian injection. The effects of ovarian function and fertility ability were measured and compared among different groups after transplantation.Results: Intraovarian transplantation of PBMCs alone or in combination with PRP resulted in restoration of the normal estrus cycle, consistent with recovery of serum sex hormone levels, increased follicle numbers at all stages, and restoration of fertility by facilitating pregnancy and live birth. Moreover, when combined with PRP injection, these effects were more significant. The male-specific SRY gene was detected in the ovary at all four time points, which suggested that PBMCs continuously survived and functioned in NOA rats. In addition, after PBMCs treatment, the expression of the angiogenesis-related marker VEGF and glycolysis-related molecules lactate dehydrogenase A (LDH-A) and sirtuin 1 (SIRT1) in NOA-overexpressing cells was upregulated, which indicated that these effects were associated with angiogenesis and glycolysis.Conclusions: PBMCs transplantation can restore the ovarian functions and fertility of NOA rats by increasing ovarian vascularization, folliculogenesis and glycolysis, and PRP could enhance the efficiency. However, more studies are required to evaluate the feasibility, safety, and efficacy of these novel fertility-preserving methods.