AIM: To develop a competency assessment instrument for nurses who have completed an outcome-based educational program based on national standards and to assess the content-, construct-, and criterion-related validity of that instrument. METHODS: In the development stage, the competencies of nurses with 1-3 years' clinical experience after the completion of nursing education and training programs, based on national standards, were identified. A systematic literature review was conducted to derive the competencies in addition to the 12 national standard competencies. In the evaluation stage, the content-, construct-, and criterion-related validity of the developed tool were verified. For verification of the content validity at each stage, the participants were 10 nurse managers of general hospitals and 10 nurse professors. A factor analysis was conducted to assess the construct validity and the Cronbach's alpha coefficients and item-total correlation were used to assess the reliability of the developed scale. For the factor analysis, the participants were 141 nurses with 1-3 years' clinical experience who were recruited from four general hospitals. In order to evaluate the construct- and criterion-related validity, the correlations between a nursing performance measurement scale, a self-leadership tool, and the developed scale were examined. RESULTS: A competency assessment instrument, consisting of 19 items on a 4-point scale, was developed and validated for assessing the competencies among nurses with 1-3 years' experience. CONCLUSIONS: Nursing research, policy awareness, and leadership competencies were required by the Korean Accreditation Board of Nursing Education for nursing college graduates, but were removed due to poor content validity, indicating a need for nursing professionals to bridge the gap between educational standards in nursing colleges and clinical settings.