Background: Nurse practitioners (NPs) play a vital role in healthcare, particularly in acute care settings in Taiwan. The professional competencies of NPs are essential for providing safe and effective care to patients. To date, no measurement tool is available for assessing the clinical competencies of NPs in acute care practices.

Purpose: The aim of this study was to develop and investigate the psychometric properties of the Acute Care Nurse Practitioner Competencies Scale (ACNPCS).

Methods: Mixed-method research was employed using samples of experienced NPs. First, we used a focus group of seven experienced NPs who worked for medical centers, community hospitals, and regional hospitals to identify clinical competencies content. Second, we implemented consensus validation using two rounds of the Delphi study and revised it to a 39-item ACNPCS. Third, we conducted content validity with nine NP experts and modified the competency content to 36 items. Finally, we conducted a national survey of 390 NPs from 125 hospitals to determine the extent to which the NP competency content relates to their clinical practice. To examine the reliability of the tool, we tested the internal consistency reliability and test–retest reliability. Exploratory factor analysis, confirmatory factor analysis, and known-group validity were used to test the construct validity of the ACNPCS.

Results: The Cronbach's alpha coefficient for the overall scale was .92, with subscale coefficients ranging from .71 to .89. Test–retest reliability showed the two scores of the ACNPCS on the two occasions tested to be highly correlated (r = .85, p < .001). Exploratory factor analysis revealed that the scale had six factors: providing healthcare, evaluating care, collaboration, education, care quality/research, and leadership/professionalism. Factor loadings for each factor item ranged from .50 to .80 and explained 72.53% of the total variance in the NPs' competencies. Confirmatory factor analysis indicated that the six-factor model showed satisfactory model fit (χ2 = 780.54, p < .01), and the fit indices met the standards for adequate fit (goodness-of-fit index = .90, comparative fit index = .98, Tucker–Lewis index = .97, root mean square error of approximation = .04, and standardized root mean residual = .04). Known-group validity revealed that the total scores for novice NPs differed significantly from those of expert NPs in terms of the competencies (t = 3.26, p < .001). These results validated the psychometric soundness of the newly developed ACNPCS.

Conclusions: The newly developed ACNPCS exhibited satisfactory reliability and validity, supporting the use of the ACNPCS as a tool to assess the clinical competencies of NPs in acute care settings.