Background: Operation rooms are one of the most hazardous environments in terms of possible human-related health hazards , identifying the contributing factors is a necessity to reduce the errors and improve the quality of health care.. Aim: this study aims to explore the nursing errors in operating room as perceived by nurses under study, investigate the factors affecting them and suggest Preventive guidelines regarding their prevention. Study design: cross-sectional descriptive research design was utilized in this study to fulfill the aim of the study and answer the research question. Subject: convenient sample include all available (96) nurses who works at operating rooms in the three previously mentioned hospitals and agree to participate voluntarily in the study. Setting: The study was conducted at operating theatre at the three hospitals from 3 geographical governorates including; Mansoura university hospitals, Port Said Health insurance hospitals and Ain shams university hospital. Data collection tools: Semi-structured nurses' interview questionnaire to investigate the nursing errors in operating room and explore factors affecting its occurrence as perceived by nurses under study. It consists of three parts including; assessment of demographic and general characteristics of the nurses under study, assessment of nursing errors in operating room as perceived by nurses under study and assessment of the factors affecting occurrence of nursing errors in operating room as perceived by nurses under study. Results: it was found that 72.9%, 67.7 % and 62.5% of the studied nurses agree that  lack of appropriate equipment, poor aseptic technique in skin preparation/handling/ draping and inadequate documentation process respectively were common nursing errors in OR setting. The results showed that the most common reported human factors which were arranged in descending order as communication system-related factors (77.3%) and training/ supervision related factors (58.46%). Regarding environmental domain, it was found that the most common reported factors as perceived by studied nurses were material and equipment resources / maintenance (79.33%). Recommendations: All operating room nurses should participate in training programs to increase their knowledge and practice, as well as to reinforce positive attitudes towards patient safety and error minimization.