To identify the determinants of the quality of nursing care from the perceptions of nursing personnel. The quality of nursing care is often measured with standards, expectations, satisfaction and outcomes, but in developing countries, it relies mostly on negative indicators. A descriptive qualitative study was used. Semi-structured interviews based on the critical incident technique were conducted with a convenience sample of 136 nursing personnel who told 225 stories. Seven quality determinants of nursing care were identified as follows: standard of care, triage and assessment, emergency care, communication with the patient or family, communication with colleagues, multidisciplinary teamwork and helping colleagues. The most important one was the standard of care. Quality nursing care is based on the degree of excellence nursing personnel show with regard to their competences in technical care, communication and teamwork. A key attribute of quality nursing care is defined by the related standards, and the focus is mostly on the nursing care process. These findings can increase awareness of the determinants of nursing quality and the qualities of the nursing personnel involved and can help managers to evaluate nursing practice, select new employees and organise teams. © 2020 John Wiley & Sons Ltd.