This exploratory study aims to extend and strengthen the empirical case for supervision as a facilitator of professional growth, as outlined in an established conceptual model, by exploring its correlates among psychotherapists across their entire professional career. Ratings of the impact of supervision by 6267 psychotherapists of different professions, theoretical orientations, and career levels in many countries who were currently in supervision were correlated, separately for each of five career cohorts, with aspects of their treatment experience, work situation, and personal characteristics. Large percentages of psychotherapists at all career levels, including senior psychotherapists, engaged in supervision and rated its impact on their development positively. Growth-facilitating supervision was associated broadly but moderately in all career cohorts mainly with interpersonal aspects of therapists’ treatment experience, with supportive work settings, and with caring and expressive personal characteristics. Some differential findings among cohorts also reflected potential developmentally based functions of supervision. The implications of results were considered both for supervisory practice, training and for future supervision research.