Tehran University of Medical Sciences Journal of Pharmaceutical Care 2322-4630 9 1 2021 04 04 3 12 Serajaddin Gray Deptartment of Health Management and Economics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. Mohammad Effatpanah School of Medicine, Ziaeian Hospital, International Campus, Tehran University of Medical Sciences, Tehran, Iran. Sara Salehi School of Medicine, Ziaeian Hospital, Tehran University of Medical Sciences, Tehran, Iran. Siamand Anvari Savojbalaghi School of Medicine, Roozbeh Hospital, Iinternational Campus, Tehran University of Medical Sciences, Tehran, Iran. Leila Momeni School of Medicine, Ziaeian Hospital, Tehran University of Medical Sciences, Tehran, Iran. Roghayeh Abedi Gilavandani School of Medicine, Ziaeian Hospital, Tehran University of Medical Sciences, Tehran, Iran. Alireza Abbasi Chaleshtari School of Medicine, Shariati Hospital, Tehran University of Medical Science, Tehran, Iran 2021 02 07 2021 02 08 Background: Given the special importance of preventing from medication, the present study aimed to investigate the determining Causes of Medication Errors (CMEs) and their Priorities for reducing interventions in a hospital.Methods: The present mixed, sequential and cross-sectional study was conducted in a teaching hospital (2016). For data collection, Fishbone Diagrams, interviews, note taking and checklists were used, and qualitative data were analyzed though the thematic approach. Moreover, the Maxqda Software v.14.0, Excel, Edraw Max v.9.0 were employed for data analysis and reporting.Results: Seventy-five CMEs were classified under two main themes (human and non-human) and four sub-themes (personal, network, organizational, and meta-organizational). Weakness of professionalism and low experience as the personal causes; Actions of pharmacy colleagues, physicians and other nurses as the network causes; Management of nurses and unit specialty as the organizational causes and the quality of academic education, drug features and macro policies of medication as meta-organizational causes were classified. Six causes were given priority for reducing interventions.Conclusion: In the short term, human factors should be considered with the aim of reducing medication errors. It is also recommended that teaching how to deal with nurses’ stress and psychological pressure (especially beginner nurse), resulting from critically ill patients and high workload, be paid special attention. Besides, it is suggested that professionalism be given priority to reduce personal neglects and to create safe environments for reporting personal neglects. In addition, more emphasis should be placed on the right route in the process of medication administration. https://jpc.tums.ac.ir/index.php/jpc/article/view/407