Aim: To define the competencies of nurse anaesthetists in the hospitals of Catalonia on the basis of their clinical practice through a consensus-building process. Design:We used the Delphi method to determine consensus among a group of 16 nurse anaesthetists. Methods:Between February and June 2020, we administered a questionnaire of 142 questions distributed among seven domains: expert, communicator, collaborator, manager, health advocate, scholar and professional. Two rounds were conducted. Results:In round 1, 18 competencies were discarded and nine had inconclusive results. Eighteen competencies were proposed by participants. The nine competencies with inconclusive results and the 18 newly proposed competencies were considered in round 2. In round 2, three of these 27 competencies tested were discarded, and consensus was reached on the other 24. Conclusion:Health education and the empowerment of the patient and family are fundamental pillars in the practice of nurse anaesthetists in Spain, especially in pre-anaesthetic assessment and pain care. These areas of practice can help define competencies in other countries where the profession of nurse anaesthetist is less developed. Impact:The lack of regulation of the competencies of nurse anaesthetists leads to great variability in training and practice. The results can help in their standardization in Spain and in other countries lacking regulation. Our approach can also help policymakers and hospital administrators in health systems that are undergoing the process of regulation. The regulation of the competencies of nurse anaesthetists will allow them to contribute their expertise to the health-illness continuum, increasing safety and improving the quality of care.