Abstract Background The demand for critical care nursing is increasing globally, including in China, where nurses in intensive care units and general wards manage critically ill patients. However, no locally validated tool exists to assess their practical competency in this field. Objective To develop and validate a Critical Care Practical Competency Scale for Clinical Nurses in China (CCPCS-CN) based on the Knowledge–Attitude–Practice framework. Methods A mixed-methods sequential design was used. Phase 1 generated items via literature review, interviews, focus groups, and a Delphi survey. Phase 2 involved a cross-sectional survey of 796 nurses from tertiary hospitals for item analysis and exploratory factor analysis (EFA). Phase 3 used confirmatory factor analysis (CFA) to validate the structure and assess reliability and validity. Results The final CCPCS-CN has 22 items across three dimensions: Foundational Critical Care Skills (13 items), Proficiency in Operating Equipment (5 items), and Capability for Collaborative Emergency Response (4 items). EFA indicated a three-factor structure explaining 72.6% of variance. CFA confirmed good model fit  (\upchi 2/df=3.4, CFI=0.93, TLI=0.92, RMSEA=0.07)\:({\upchi\:}^2/\text{d}\text{f}=3.4,\:\text{C}\text{F}\text{I}=0.93,\:\text{T}\text{L}\text{I}=0.92,\:\text{R}\text{M}\text{S}\text{E}\text{A}=0.07) . The total scale of Cronbach’s alpha was 0.94 with sub-scales being 0.93, 0.88, and 0.86 respectively. Value of Cronbach’s alpha above 0.70 indicates acceptable reliability. The composite reliability and average variance extracted were good; this demonstrates that there is good convergent validity. Conclusion The CCPCS-CN is a valid and reliable instrument for determining clinical practice competency amongst nurses working in Chinese tertiary hospitals facilities. The tool will assist in identifying educational needs, evaluating education programs, and supporting workforce planning. Clinical trial number Not applicable.