Competence is of paramount importance to training in professional psychology, yet little research has addressed the development of psychometrically sound instruments for assessing competence, despite repeated calls for work in this area. Many current graduate school and internship training programs rely on cumulated hours of supervised clinical training and successful coursework completion as indicators of graduate student success, indicators that are widely regarded as poor proxies for the valid assessment of actual competence (Fouad et al., 2009). The present study aimed to address this gap by developing a measure that follows from one of the leading conceptualizations of competence in the field of professional psychology today. Results from an exploratory factor analysis of 491 psychotherapists revealed three related domains of professional competence: foundational, functional, and continuing competencies. These results were later used as a guide for confirmatory factor analyses (CFAs) with cohorts of 471 board-certified psychologists and two samples of predoctoral interns and fellows (N = 647 and 264). Results from the CFAs led to a 10-item Professional Competencies Scale (PCS) with excellent fit and strong reliability and validity (see ). Current limitations of the instrument are noted and recommendations are explored in relation to the domains of training and practice, with attention to the important role of a continuing commitment to ongoing professional development.