Introduction: This study aimed to emphasize the challenges in the error reporting system as one of the professionalism codes in clinical settings in hospitals affiliated to Tehran University of Medical Sciences, Tehran, Iran. Materials and Methods: In total, 23 focused group discussion sessions were conducted with 85 faculty members, assistants, and interns, as well as 165 staff members in 2016. The participants were selected using a purposeful sampling method. Furthermore, the views of four faculty members were gathered again via emails in 2020 to ensure data accuracy. The extracted codes were managed using conventional content analysis through MAXQDA software. Results: Analysis of participants' discussions led to the identification of 105 codes, which were classified into six sub-categories and two main categories, including "barriers to reporting errors of peers " and "barriers to self-reporting errors". Conclusion: Most of the non-reporting errors are due to participant’s concerns. Such concerns are generally the result of poor system management or are merely misunderstandings; accordingly, errors' addressing only requires gaining a person's trust. The seriousness of the system in persuading people to report errors is one of the most important ways to gain a person's trust.