Objectives: To develop and validate a new tool intended for measuring self-reported professional competenceamong both nurse students prior to graduation and among practicing nurses. The new tool is based on formalcompetence requirements from the Swedish Board of Health and Welfare, which in turn are based on WHOguidelines.Design: A methodological study including construction of a new scale and evaluation of its psychometricproperties.Participants and settings: 1086 newly graduated nurse students from 11 universities/university colleges.Results: The analyses resulted in a scale named the NPC (Nurse Professional Competence) Scale, consisting of 88items and covering eight factors: “Nursing care”, “Value-based nursing care”, “Medical/technical care”, “Teaching/learning and support”, “Documentation and information technology”, “Legislation in nursing and safetyplanning”, “Leadership in and development of nursing care” and “Education and supervision of staff/students”.All factors achieved Cronbach's alpha values greater than 0.70. A second-order exploratory analysis resulted intwo main themes: “Patient-related nursing” and “Nursing care organisation and development”. In addition,evidence of known-group validity for the NPC Scale was obtained.