Background: Repeated implantation failure has been one of the concerns in ICSI in recent years. It's linked to maternal or embryonic influences. One of the maternal factors is chronic endometritis (CE) which may affect the outcome of ICSI and so, its treatment may improve the results of ICSI. Objectives: To evaluate the effect of chronic endometritis treatment on the outcome of ICSI in repeated implantation failure (RIF). Methods: This is a prospective study conducted at the International Islamic Center for Population Studies and Research, Al-Azhar University on 120 patients with RIF. Patients were scheduled for hysteroscopic endometrial biopsy with histopathological examination. If there was no evidence of CE, the patients were scheduled for ICSI directly (Group A). Patients with CE received antibiotics and endometrial biopsy was done in the next cycle. According to the result of the second biopsy, patients were divided into 2 groups: - Patients with cured CE (Group B) and patients with persistent CE (Group C). We compared the chemical pregnancy rate, clinical pregnancy rate, and the miscarriage rate in study groups. Results: Patients with cured chronic endometritis had a significant higher chemical and clinical pregnancy rate compared with patients with persistent chronic endometritis (43.5% vs. 17.9% and 39.1% vs. 10.7% respectively). The miscarriage rate was higher in patients with persistent CE than other groups but with no significant difference. Conclusion: Treatment of chronic endometritis improved the outcome of ICSI regarding the chemical and clinical pregnancy rate.