To assess the prevalence of chronic endometritis (CE) among women with non-uniform endometrial echogenicity, and to evaluate the association between CE and metabolic characteristics as well as pregnancy outcomes in the subsequent frozen-thawed embryo transfer (FET) cycles. Retrospective cohort study. University-based hospitals and an academic medical center. A total of 315 patients included in this research underwent hysteroscopy and endometrial biopsy before the first FET cycle after whole embryos freezing. Patients were divided into CE (histopathologic CE or hysteroscopic CE) and non-CE groups. Freeze-all strategy, hysteroscopy and endometrial biopsy. Baseline and cycle characteristics, hysteroscopic, and histopathological profile, as well as pregnancy outcomes. The prevalence of histopathologic CE and hysteroscopic CE were 78.1% and 34.9%, respectively. CE was associated with higher homocysteine level and BMI, independent of insulin response and dyslipidemia. High homocysteine level and BMI were risk factors for histopathologic CE (OR: 1.182; 95% CI: 1.01-1.384; p=.037) and hysteroscopic CE (OR: 1.117; 95% CI: 1.041-1.199; p=.002), respectively. Histopathologic CE was a risk factor for live birth (OR:2.167; 95% CI: 1.037-4.525; p=.04), and hysteroscopic CE was an independent risk factor for both live birth (OR: 4.239; 95% CI: 1.929-9.313; p=.001) and cumulative live birth (OR: 3.963; 95% CI: 1.875-8.376; p=.001). Infertile women with non-uniform endometrial echogenicity have a high prevalence of CE which significantly reduces the live birth rate. Diagnosing CE by hysteroscopy is important to assess the cumulative probability of pregnancy in IVF patients.