Background: Poor responders constitute a less fortunate group of patients attending any IVF/ICSI clinic. Identifying these patients helps in choosing the most appropriate stimulation protocol. Aim:This is a randomized controlled prospective study that aimed to study the effect of adding letrozole to GnRH antagonist protocol in poor responders undergoing ICSI. Materials and Methods: This study was carried out on a sample of 70 infertile couple, thirty five patients in each group, five cases were canceled in group I (letrozole/antagonist group), while six patients in group II (antagonist group) canceled the cycle. In group I, letrozole 5mg was given from day 2 cycle for 5 days. Initial dose of HMG 300 I.U from day three cycle, then the dose was modulated according to response in both groups and ICSI was done. The women were followed to detect the occurrence of pregnancy by measuring serum B-hCG 14 day after embryo transfer and clinical pregnancy was followed up at 6th week of gestation. Results: The dose of HMG was significantly lower in group I than in group II, while there were no significant statistical differences in the duration of stimulation, number of oocytes retrieved, fertilization rate, implantation rate, cycle cancelation rate, and clinical pregnancy rate with adding letrozole to GnRH antagonist cycles in women with POR. Conclusion:Letrozole is recommended to be added to ICSI stimulation protocols in poor responders. Although it didn't affect the pregnancy rate, letrozole decreases the dose and the cost of ICSI cycles.