Background: Nursing competence is an essential element in ensuring high-quality nursing care and positive patient outcomes. Valid and reliable assessment tools for assessing nurse competence are needed to help nurse supervisors measure whether nurses are performing their job well and to provide a baseline for improving the competences of nurses. Purpose: This study was designed to develop and psychometrically validate the Competence Scale for Clinical Nurses (CSCN). Methods: The CSCN was developed in three steps: (a) generalize assessment items from nursing competence-related scales and a review of the relevant literature, (b) determine the content validity of the developed scale, and (c) psychometrically test the developed scale. Five hundred nurses were recruited from a medical center in southern Taiwan. Exploratory and confirmatory factor analyses were executed to analyze construct validity and internal consistency reliability. Results: The scale-content validity index was .87, as determined by five experts. Two thirds (63.29%) of the variance was explained by three factors: basic care skills (nine items), being dedicated to work (five items), and patient-centered and ethical considerations (four items). A second-order confirmatory factor analysis indicated that the data fit the model well. The Cronbach's alpha coefficients for each of the three factors and the total scale were .84-.91. Conclusions/Implications for Practice: The 18-item CSCN is a feasible and time-efficient tool for assessing competence in clinical nurses. Nursing supervisors may use this tool to explore nurses' competency and routinely track the effect of continuing education on competence. Continuous evaluation of nurses' clinical-based competence using the CSCN is recommended.