Background Core competencies of intensive care unit (ICU) nurses were defined as the essential capability to influence patient safety and interdisciplinary collaboration; however, there has been no research conducted that relates to core competencies of ICU nurses at Chinese tertiary‐A hospitals in Shanghai. Aims and objectives To investigate the current state of core competencies and the factors that influence this key capability in ICU nurses in Chinese tertiary‐A hospitals. Design This was a multicentre, cross‐sectional study. Methods A convenient sampling method was used to investigate 451 ICU nurses at five tertiary‐A hospitals in Shanghai. Data were collected using self‐administered questionnaires. Results The core competencies of ICU nurses were above average, and the scores of seven dimensions, ranked from first to last, were medical ethics, clinical practice, nurse–nurse co‐operation, assessment and decision‐making, personal and professional development, teaching and research and nurse–physician co‐operation. Multivariate linear regression analysis showed that the factors exerting an influence on the core competencies of ICU nurses were title, role incumbent and ICU department. Conclusion This study showed an above‐average level of core competencies among ICU nurses in tertiary‐A hospitals in Shanghai; however, competencies related to nurse–physician co‐operation and the translation of research into practice were underdeveloped. Relevance to clinical practice Nursing managers should implement targeted interventions to improve nurse–physician co‐operation and translate research into practice competencies, such as high‐fidelity simulation, inter‐professional education, scientific research training and innovative skills tutorials. Moreover, this study demonstrated the influencing factors that can be used to improve core competences of ICU nurses.