Development and Exploratory Validation of the Clinical Research Nursing Competencies-Self-Efficacy Scale

<b>Background/Objectives</b>: The objective of this study was to develop and validate the Clinical Research Nursing Competencies-Self-Efficacy (Se-CRN) scale, a theory-grounded instrument to assess perceived capability in clinical research nursing practice. <b>Methods</b>: A two-phase validation study was conducted using an exploratory sequential mixed-method design between July 2022 and September 2025. The initial item pool was derived from an established competency taxonomy and refined through expert review for face and content validity. The final version of the Se-CRN was administered online to Clinical Research Nurses working with patients enrolled in clinical trials in Italy. Structural validity was examined using exploratory factor analysis with parallel analysis, and reliability was assessed through internal consistency and hierarchical indices. Group differences in self-efficacy were examined across clinical settings, educational levels, and research experience. <b>Results</b>: A total of 183 nurses participated. The data supported a five-factor solution reflecting core dimensions of clinical research nursing (Clinical Practice, Study Management, Human Subject Protection, Contributing to the Science, and Care Coordination and Continuity). Reliability was excellent at the scale level and strong across domains. No differences in perceived capability were observed between oncological and non-oncological settings. Higher self-efficacy was consistently associated with greater experience in the research setting and, to a lesser extent, with advanced education. <b>Conclusions</b>: The Se-CRN is the first validated self-efficacy instrument that captures the full scope of clinical research nursing practice. It provides a practical measure to support training needs assessment, curriculum development, and workforce planning. Further research should confirm the factor structure and examine responsiveness to professional development across diverse settings.