Purpose To develop a methodology for identifying the universal nursing competencies required for registered nurses (RNs). Design A mixed‐methods approach was used. Methods The research in this article entails a combination of different methodological approaches, namely the Delphi technique and an empirical quantitative nonexperimental study. A total of 14 experts with credentials in the nursing field participated in the former. Consensus was defined as at least 80% agreement. Subsequently, a purposive sample of 321 RNs participated in the empirical quantitative nonexperimental study. The data were collected during 2014. Findings In the study's first stage, 39 professional nursing competencies were identified using the Delphi technique. In the second stage, factor analysis resulted in seven factors: professional nursing clinical practice; professional communication and quality in nursing; determinants of health and safety in nursing; critical thinking and self‐planning of professional work; new knowledge and knowledge transfer in nursing; management and coordination in nursing; and nursing research. Together they explain 74.9% of the variance. Conclusions and Clinical Relevance In the future, the identification of the national nursing competencies should be considered. The study has some limitations; however, the proposed methodology revealed in this study may be the first step in overcoming them.