Purpose: To evaluate the effect of the premedication with dehydroepiandrosterone (DHEA) on the results of the in vitro fertilization (IVF) treatments in a group of women with evidence of diminished ovarian reserve. Materials and Methods: This experimental, prospective, pre-post study enrolled 29 patients with evidence of diminished ovarian reserve and poor-responders to a previous treatment. They received 75 mg/die of DHEA for a minimum of eight weeks; from the 18^th day of the cycle before the stimulation with follicle stimulating hormone (FSH), they took trans-dermal estradiol (E2) (50 mcg every other day). The protocol of the stimulation consisted of a short cycle with follicle stimulating hormone receptor-human menopausal gonadrotropin (FSHr-HMG) and low doses of gonadotropin releasing hormone agonist (GnRH-a) (0.05 mg/die). The study was carried out comparing the results obtained respectively with the pre-DHEA and the post-DHEA treatments. Results: The comparative analysis of the results showed a significant increase in the number of the retrieved oocytes (p < 0.01), of the oocyte quality (p = 0.02) and a reduction of cancelled cycles (p = 0.03). Moreover, after the treatment with DHEA, there was an increase, though non-significant, in the number of embryos, in the fertilization rate, and in the number of pregnancies. Conclusions: This study confirms the beneficial effects of DHEA in patients who resulted poor responders to IVF treatments. Therefore, DHEA appears to be an effective treatment for age related sub-fertility.