Objective. Medication errors are the most common types of medical errors which considerably endanger the patient safety. This survey aimed to study the factors influencing not reporting on medication errors from the nurses' viewpoints in Abbasi Hospital of Miandoab, Iran. Methods. This was a cross-sectional, descriptive and analytical study conducted in 2012 in which all nurses (n = 100) working in different inpatient units were studied using a consensus method. Required data were collected using a questionnaire. Collected data were analyzed through some statistical tests including Independent t-test, ANOVA, and chi-square. Results. According to the results, the most important reasons for not reporting on medication errors were related to the managerial factors (3.56 ± 0.996), factors related to the process of reporting (3.32 ± 0.797), and fear of the consequences of reporting (3.01 ± 1.039), respectively. Also, there was a significant relationship between employment status and fear of the Consequences of reporting on medication errors (P < 0.008). Conclusion. This study results showed that managerial factors had the greatest role in the refusal of reporting on medication errors. Therefore, for example, establishing a mechanism to improve quality rather than focus only on finding the culprits and blaming them can result in improving the patient safety.