Increasing healthcare system complexity, multidisciplinary care delivery, and the need to deliver high-quality, cost-effective care drive a critical need for leadership development. Currently, few examples of multidisciplinary leadership development exist in the medical education literature. The Accreditation Council for Graduate Medical Education (ACGME) has identified leadership domains as essential milestones in residency education, encompassing areas such as interpersonal communication, quality improvement, and systems-based practice. Presently, published GME leadership curricula vary widely in content, delivery, and duration and rarely include multispecialty cohorts. The study authors designed and implemented a longitudinal leadership curriculum for a multispecialty cohort of senior residents and fellows from multiple hospitals within a large integrated GME program. Between July 2022-June 2023, authors delivered 12 monthly sessions on core leadership concepts. Sessions delivered relevant work-based content via large-group didactics with embedded opportunities for small-group interactive experiential and reflective practice, critical thinking, and application. Thirty GME trainees participated in the longitudinal curriculum. Interval pre-/post-session assessments demonstrated significant improvement in composite scores for 6 of 9 sessions assessed. Participants rated each module's overall importance, applicability, and acceptability highly on a summative program evaluation. This longitudinal leadership curriculum adheres to best leadership development practices, demonstrates improvement in knowledge and self-reported attitudes and behaviors related to cognitive, character, and emotional leadership domains, and develops a psychologically safe community of practice for GME participants.