The quality of health care and patient safety in the operating room is a major concern for nurse anaesthetists. However, few studies have focused on the experiences of nurse anaesthetists’ and their contributions to safety in this setting. Therefore, this study aims to explore the content and frequency of incidents reported by nurse anaesthetists in the operating room and the risks involved in these incidents. A retrospective study with a descriptive design was conduct. Data were gathered concerning 220 incidents reported by nurse anaesthetists from 2012 to 2015 in operating rooms at a middle-sized hospital in Sweden. These were analysed with a method for qualitative and quantitative content analysis. The findings are presented in five categories: communication and teamwork; routines and guidelines; patient care; nurses’ work environment; devices, materials and technologies. In 184 (73%) of the incidents, there was either a risk of harm or there was an actual harm to patients or nurses. Of all incidents only 23 (10%) had harmed patients or nurses. Few of these incidents involved patient harm (n = 6), while a greater number involved harm to nurses (n = 17). The findings reveal lack of communication and interprofessional teamwork as the two most common areas for the reported incidents, followed by problems related to lack of compliance with guidelines and routines. The findings suggest that strategies are needed to improve these areas. Patient safety reporting systems may be important to identify risk in preventing patients and health care professionals from being harmed. In addition, the findings indicate that the nurses sought to prevent harm to patients rather than to themselves. Consequently, increased attention to the work environments of nurses, and most likely other professionals, in the operating room may be needed to prevent health care professionals from being harmed.