Background: Medical errors frequently occur in healthcare facilities, jeopardizing patient safety and increasing associated costs. Aims: This cross-sectional investigation examined the rates of and reasons for non-reporting of medical errors at Nemazee Hospital, Shiraz, Islamic Republic of Iran. 1 / 12 WHO EMRO | Prevalence of non-reporting of hospital medical errors in the Islamic Republic of Iran Methods: Self-administered questionnaires were completed by 283 staff members, including physicians, nurses and medical students. One-way analysis of variance (ANOVA), Fisher's Least Significant Difference (LSD) post hoc, Spearman Correlation Coefficient and Intra Class Correlation (ICC) tests were used for statistical analyses. Results: Almost all (95.8%) of participants had observed at least one medical error during the previous year. Over half (50.5%) had observed three to ten medical errors in the last year. The preferred method for reporting medical errors among physicians and medical students was verbal and informal (40.3% and 41.8%, respectively), while nurses preferred written forms (45.7%). The results indicated significant differences between groups concerning individual and organizational barriers in general and among all sub-categories (P < 0.001). Conclusion: Concerns of legal entanglements and confidentiality issues were recognized as main barriers to reporting medical errors.