ABSTRACT Introduction & Objective: To study whether intrauterine granulocyte colony stimulating factor (G-CSF) improves the rates of clinical and ongoing pregnancy and live birth rates in unexplained repeated implantation failure (RIF) patients on their new ICSI-ET program. Study Design: In University affiliated, Avicenna specialized center for fertility and repeated miscarriages 93 consenting unexplained RIF patients with normal endometrium and without any history of malignancy or uncontrolled background disease were enrolled in a registered, computer generated randomized double blinded placebo-controlled clinical trial. Patients underwent intrauterine perfusion of G-CSF or Placebo before ET and were monitored to calculate the Clinical & ongoing pregnancy and live birth rates in each group. Result: The mean age was 32.85±5.02 years in G-CSF and 33.57±4.63 years in placebo group. There were no differences in baseline characteristic of patients and the ICSI protocols in groups. clinical and ongoing pregnancy and live birth rates were 17%, 14.9% and 12.8% in G-CSF group and 21.4%, 17.4 %and 13 % in control group respectively and did not show any statistically significant difference between the two groups. No adverse side effect was seen in the study groups. Conclusions: In the study, intrauterine G-CSF did not affect clinical and ongoing pregnancy and live birth rates There was a non- significant improvement in clinical and ongoing pregnancy rate and also a reduction in the first trimester abortion in GCSF patients. Non-significant higher ongoing pregnancy and lower abortion rates in the G-CSF group may be due to limited sample size or low G-CSF dosage. So further multicenter studies with larger sample size or higher doses of G-CSF is recommended. Clinical Trial Registration Number: IRCT2013063011653N2.