Various natural antioxidants, such as spirulina platensis (SP) as dietary additives, are beneficial to attenuate the detrimental effects of oxidative stress on fertility of females. The present study targeted to investigate:1) dietary SP effect (200 and 400 mg/kg LBW) on the reproductive performance, ovulatory responses and embryos development, and 2) effect of liquid SP addition to culture media (0.05 and 0.1 ml/ml) on in vitro embryos development of NZW rabbit does under heat stress. Results revealed that both dietary SP additions led to an increase (P<0.05) in ovarian weight, relative ovarian weight, total, antral follicles and CLs numbers, ovulation rate, and number and percentage of expanded blastocyst and hatched blastocysts, while decreased (P<0.05) number of bleeding follicles, number and percentage of degenerated embryos compared with control group. In vitro embryo developmental competence, in terms of number and percentage of hatched blastocysts increased (P≥0.05) by SP compared to control. Number and percentage of expanded blastocysts and degenerated embryos decreased (P≥0.05) in treatment groups as compared to control group. In conclusion addition of SP at a level of 400 mg/kg LBW in the diet of rabbit does improved reproductive traits in terms of increasing site and rate of ovulation, yield of acceptable embryos, and hatched blastocyst production. However, in vitro addition of SP in culture medium had no pronounced effect on the developmental competence of rabbit embryos.