Background The cause of infertility has not been found in unexplained infertile patients,, and perhaps one of the possible reasons is impairment of fetal implantation, as well as the multiple role of GCSF in improving implantation and quality of blastocyst. Therefore, the aim of this study was to investigate the role of GCSF in the pregnancy rate of patients undergoing IUI.Methods The patients with unexplained infertility were divided into two groups: one group was received GCSF in their IUI cycle and the other group had the routine IUI. Both groups were stimulated by letrozole, metformin, and monotropin during the cycle. When at least one follicle was greater than 18 mm, 5000 IU hCG intramuscularly was administered for ovulation induction and IUI was performed 34–36 hours later. In intervention group, 300 ug GCSF subcutaneously administrated in two days after IUI. Biochemical pregnancy rate was evaluated two weeks after IUI and clinical pregnancy rate was identified by the presence of a gestational sac on ultrasonography 8 weeks after IUI.Results There was no significant difference in demographic and clinical characteristics between the two groups. The chemical pregnancy rate(16.3% vs 12.2%) and the clinical pregnancy rates (16.3% vs 8.3%) were improved in patients receiving GCSF compared to controls, but these differences was not significant (P = 0.56) and (P = 0.21).Conclusion Systemic administration of a single dose of 300 µg GCSF subcutaneously two days after IUI may slightly improve clinical pregnancy rate in patients with unexplained infertility. Nevertheless, our findings do not support routine use of G-CSF in unexplained infertility women with normal endometrial thickness.