Background: Some studies reported the association between fibroids with uterine inflammation. By considering this hypothesis, the formation and recurrence of uterine fibroids can be prevented by diagnosis and treatment of inflammation, and complications and costs can be reduced. This study aimed to evaluate the association between chronic endometritis and uterine fibroids in non-menopausal women. Materials and Methods: This prospective case-control study was performed on non-menopausal women referred to Al-Zahra Hospital in Rasht during April 2019-April 2020. Non- menopausal women of reproductive age (20-55 years old) with abnormal uterine bleeding who were candidates for hysteroscopy based on medical history and ultrasound reports were included in this study. The case group with fibroids were divided into two groups of intramural and subserosal myoma group and submucosal group based on the location of fibroids. The control group was patients with abnormal uterine bleeding complaints and no uterine fibroid. Endometrial specimens were examined by a pathologist for histological and immunochemistry assessments. In interpreting the results of endometrial biopsy, a positive result was indicated by the presence of one or more plasma cells per 10 high power field. Data were gathered by a form including age, parity, history of recurrent miscarriage, patient’s complaint (abnormal uterine bleeding), hysteroscopic results (submucosal myoma-polyp-normal), uterine histology (polyp, endometritis, and hyperplasia) and prevalence of chronic endometritis based on plasma cell in the biopsy. Data were analyzed by SPSS software version 21. Data were reported by descriptive statistics including number, percent, mean and standard deviation. The normality of quantitative data was assessed by the Kolmogorov- Smirnov test. Mann-Whitney U test, Chi-square and Fisher exact tests were used to compare groups and logistic regression was used to control the effect of confounders. Results: The incidence of chronic endometritis was 39% (38 out of 97) and a higher incidence of chronic endometritis was noted in the case group than the control group (46% vs. 31%), No significant difference was observed between the two groups ( P > 0.05). However, the incidence of chronic endometritis in women with submucosal myoma was higher than the intramural and subserosal groups (64% vs. 37%) ( P = 0.04). To control the effect of age on the rate of chronic endometritis in both groups, no significant effect was observed in logistic regression. Conclusions: The results showed the overall incidence of chronic endometritis was higher than previous studies and also the incidence was higher and more significant in women with submucosal myoma than in the intramural and subserosal group. As in this study, authors assessed the association between chronic endometritis and uterine fibroids, further studies assessing...