ABSTRACT Objective Competency-based models of training have led to systemic and sweeping changes to psychologist training and supervision. However, this progress has mostly been in knowledge and skill competencies. Psychology currently lacks an instrument to track attitude-values changes across practitioner developmental stages. The current study describes the development and validation of the Attitude-Values for Competent Psychology Practice (AV-CoPP) scale. Method In Study 1, a set of 40 attitude-values across seven domains were selected. Content validity was examined by having each item rated for their importance by provisional psychologists (N = 61), psychologists (N = 94) and psychologists with endorsement (N = 113). Study 2 evaluated the convergent and divergent validity of the instrument by having psychology trainees (N = 92) rate the relative importance of these 40 items for psychologists, teachers, and plumbers. Results Results indicated excellent content validity and good internal reliability for the seven subscales. Further, the subscales adequately differentiated standards of professional practice expected of the three professional groups. Conclusion The research offers good preliminary psychometric support for the AV-CoPP. The AV-CoPP makes an important contribution to competency research by enabling the systematic measurement of attitude-value changes during training and supervision.