Background: Reporting errors has a key role in reducing the frequency of errors and improving patient safety. The present study was conducted to investigate factors affecting reporting of nursing errors in military hospitals. Materials and Methods: The present qualitative study was conducted with the participation of eight military nurses. Data were collected using semi-structured in-depth interviews. Sampling began purposively and continued until data saturation. Data were analyzed according to Elo and Kyngas content analysis approach. Results: Analysis of data led to the extraction of 400 initial codes and two general categories, including barriers to reporting error (error causing harm, maintaining reputation, negative organizational encounter, nurse’s temporary position, and lack of accountability) and facilitators of reporting error (positive previous experience, being new, anonymity of reporting system, nurse’ personal values, positive supportive atmosphere). Discussion and Conclusion: Many factors affect reporting errors, some facilitate and some prohibit it. To obtain proper information about errors and improve patient safety, health systems should reinforce factors facilitating reporting errors in hospitals.