This article describes an initiative to train public sector clinicians in competency-based clinical supervision. It was delivered as an 18-session course taught online to clinicians employed in departments of behavioral health in nine Southern California counties. The curriculum was co-constructed by a team of clinical supervision scholars and leaders who then served as instructors. Each two-hour meeting addressed a specific topic for which a training video had been prepared, usually featuring a member of the training team who had expertise in that topic. The second part of each meeting focused on a class member's supervision case presentation. Those presentations revealed 35 themes; the four most frequently occurring were: developing supervisees' clinical competencies, addressing countertransference and parallel process, balancing clinical and administrative supervisory roles, and addressing record keeping/paperwork. Participants' pre-to-post supervisory self-efficacy changes demonstrated a moderate effect size (Cohen's d = .46) for the training, with the greatest pre- to post-training changes being in the use of technology, multicultural competencies (awareness of oppression, bias, and stereotyping in clinical work and in clinical supervision), and contracting. They reported that the strengths of the course included an inclusive learning environment and opportunities to reflect on and apply new knowledge and skills, though they also reported struggling with the assignments and the course platform software. Lessons learned reflected the use of technology in this online program, the importance of obtaining buy-in from agency decision makers and being prepared to address challenges related to the use of direct observation in supervision, gatekeeping, and enacting the simultaneous roles of administrative and clinical supervisor.