Context: Systematic review and meta-analysis. Objective: To assess the impact of endometrial scratch injury (ESI) on the outcomes of IUI-stimulated cycles. Methods: The review was reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Two reviewers performed the literature search and independently judged the methodological quality of studies included in meta-analysis using the Cochrane Collaboration's tool for bias risk assessment. The body of evidence was assessed using GRADE methodology. Patients: Infertile women undergoing one or more IUI-stimulated cycles. Interventions: Randomized controlled trials (RCTs) were identified by searching electronic databases. We included RCTs comparing ESI (i.e. intervention group) during the course of IUI-stimulated cycle (C-ESI) or during the menstrual cycle preceding IUI-treatment (P-ESI) with controls (no endometrial scratch). The summary measures were reported as odds ratio (OR) with 95% confidence-interval (CI). Main Outcome Measures: Clinical-pregnancy rate, ongoing-pregnancy rate, multiple-pregnancy rate, ectopic-pregnancy rate, miscarriage rate. Results: Eight trials were included in the meta-analysis, embedding a total number of 1871 IUI cycles. ESI was associated with higher clinical-pregnancy rate (OR 2.27; p < 0.00001) and ongoing-pregnancy rate (OR 2.04 p=0.004) in comparison to controls. No higher risk of multiple pregnancy (OR 1.09; p=0.88), miscarriage (OR 0.80; p=0.60) and ectopic pregnancy (OR 0.82; p=0.80) was observed in patients receiving ESI. Subgroup analysis based on ESI timing showed higher clinical pregnancy rate (OR 2.57) and ongoing pregnancy rate (OR 2.27) in patients receiving C-ESI and no advantage in patients receiving P-ESI. Conclusions: Available data suggest that ESI, performed once preferably during the follicular phase of the same cycle of IUI with the employ of flexible aspiration catheters, may improve clinical-pregnancy rate and ongoing-pregnancy rate in IUI cycles. ESI does not appear to increase the risk of multiple pregnancy, miscarriage and ectopic pregnancy.