Both graduate students and their trainers are concerned with reliable and valid evaluations of trainee skills. This article reports development of a unique system to evaluate objectively the diagnostic interview competency among professional psychology graduate students. Two training outcomes, skills used in the diagnostic interview and global interview quality, and one training process, student group supervision behaviors in diagnostic seminars, were measured. Development of generic scales is described, initial results reported, and system benefits and weaknesses are noted. Recommendations for evaluating students' competency at conducting diagnostic interviews are offered to trainers and educators, and potential clinical applications are highlighted for practitioners.