Introduction: Maternity wards are of the highly sensitive wards in hospital. Errors in midwifery tasks can lead to life threatening risks for the mother and infant and higher medical costs. The present study is an attempt to qualitatively and quantitatively assess human errors in midwife staff using preventive human error analysis and engineering approach. Methods: The study was carried out as a case study in the maternity ward of Shoushtar Women Hospital. The participants were selected through convenient sampling and seven midwifery experts took part in the study. The work process in maternity ward was categorized into four categories of admittance, pre-labor, labor, and post-labor and the tasks and sub-tasks were determined based on hierarchical task analysis (HTA). Afterwards, human errors were quantified using EA technique and then, using PHEA technique a description of error in each tasks and error control solutions were provided. Results: The results clarified that the highest risks of human errors were in the tasks like cervix check, serum therapy, infant’s body check, preparing delivery equipment, and wearing personal protective equipment. Conclusion: Since, midwifery tasks are rule base and regulations and they are performed at a higher level of awareness and cognition, preventing errors entails continuous presence of a midwife next to patient’s bed along with an assistant midwife and codification of an infant examination checklist. Programming empowerment education including safety education to midwives is also recommended.