Estimates of healthy years of life lost due to mental illness are increasing, calling greater attention to the provision of effective psychotherapy services. Hypothesized to be the key mechanism through which competencies are developed in trainee clinicians and subsequent client outcomes, clinical supervision is deserving of greater attention. Drawing on a sample of supervisors, trainees, and clients from a training clinic, the present study sought to clarify the relational factors that could facilitate the asserted supervisor-client outcome link and to better understand if, and how, clinical supervisors influence client outcomes. With the exception of supervisor openness to experience, supervisor factors did not predict meaningful variance in client outcomes. Trainee extraversion and openness to experience predicted significant variance in leader-member exchange and supervisory working alliance. Dispositional trainee factors (e.g., personality) appear to impact trainee perceptions of the supervisory relationship. Implications for training and development are discussed, in addition to directions for future research.