The literature suggests that working alliance is an important predictor of clinical supervision outcomes. However, little is known about the individual factors that influence the development and maintenance of the working alliance. This study aims to explore the role of supervisor and trainee personality traits in the development of early working alliances, as well as supervisor and trainee concordance rates in the context of clinical supervision. This study used the NEO-PI-3 measure to assess personality traits and the Working Alliance Inventory-Supervisor and Trainee Versions (WAI) measures to assess working alliance ratings. Results suggest that supervisors rate the strength of their alliances as significantly stronger than trainees (p < 0.05). While no trainee personality traits were found to predict their perception of the early alliance, the openness domain was found to be significantly associated to supervisor's self-reported ratings of alliance. Implications of these findings are discussed.