Background & aim: Apart from being an immunosuppressant agent, Cyclophosphamide (CYP) has been known to induce oxidative stress, impact on gonadal cells’ DNA and reduce the fertilizing potential.Therefore, the present study was aimed to evaluate the protective effects of crocin, as a potential antioxidant on in vitro fertilized embryo developments when exposed to CYP.Methods: Thirty six mature female mice, aged 6-8 weeks, were divided into 3 groups and treated for 21 days. The control group received normal saline (0.1 ml/kg, ip/day), and sham control group received CYP alone (15 mg/kg, ip/week) and experimental group received crocin (200mg/kg, ip/day) along with CYP (15 mg/kg, ip/week). Ovarian hyperstimulation PMSG and HCG were administrated for stimulating the ovulation process. The sperms were obtained from 6 mature male mice. Animals were anesthetized to easy draw, after oocyte extraction and normal sperm and fertilization, fertilized oocytes were incubated for 120 hours in presence of HTF+4 mg BSA, and embryonic development was examined. Data were analyzed test.Results: A significant reduction were observed in a number of proper oocytes, fertilization rate, two-cell embryos and blastocysts In the sham control group, but a significant increase in the number of stopped embryos in the control group were seen. Crocin administration significantly increased the number of proper oocytes, fertilization rate, two-cell embryos, blastocysts and embryos stopped significantly decreased compared to the sham control group (p<0.05).Conclusion: The crocin therapy co-administration with CYP resulted in a significant improvement of fertilizing potential and promoted the embryo development in vitro.