BackgroundNearly 25-50% of infertile women have endometriosis. There are reports of disorders in the expression of granulocyte colony-stimulating factor (G-CSF) receptors in women with endometriosis.ObjectiveTo examine the effect of intrauterine administration of G-CSF in in vitro fertilization (IVF) cycles on the fertility rate of infertile women with moderate-to-severe endometriosis.Materials and Methods This clinical trial was conducted on 66 infertile women with moderate-to-severe endometriosis, undergoing IVF and intracytoplasmic sperm injection (ICSI). The participants were allocated into two groups via simple randomization: the G-CSF (n = 27) and control (n = 39) groups. In the G-CSF intervention group, on the oocyte pick-up day, immediately after an ovarian puncture, 300 μg of G-CSF was injected through a transcervical catheter under abdominal ultrasound guide to visualize flushing into the uterine cavity. Women in the control group received no intervention. The two groups were evaluated for clinical pregnancy.ResultsNo significant difference was noted in the demographic characteristics of the two groups. The rate of clinical pregnancy was 28.2% in the control group and 25.9% in the G-CSF group, indicating no significant difference (p = 0.83).ConclusionThe results showed that the intrauterine injection of G-CSF had no effects on pregnancy in women with stage-3/4 endometriosis undergoing IVF.