Leadership development (LD) plays a significant role in achieving high-quality performance and business results, but there is little research on how leadership development itself evolves as the organization develops. This study explores how a leadership development system evolved over 30 years, during a time when the organization became increasingly high performing. Through reflexive thematic analysis of organizational documents and interviews with top managers and practitioners, the study provides a rich longitudinal description of the evolvement. The results revealed three pervasive changes of the leadership development system: 1) from a system for business-specific learning to one for system-wide learning; 2) from a system for personal development to one for customer-oriented quality development; and 3) from a leadership development system consisting of leadership development programs to one that is integrated into regular meetings and uses simple rules. These changes supported the gradual transformation of the leadership development from being independent to becoming integrated in the wider system, supporting the business system. The findings offer a unique insight into how an organization transitioned from individual leader development towards promoting collective aspects of leadership development. The study provides two main theoretical contributions that support the perspective of viewing leadership development as integrated within organizational development. Firstly, we present a more multifaceted way of understanding leadership development, wherein managers and employees, customer outcomes, and business advancement are seen as mutually developing. Secondly, we introduce two new critical points that complement previous descriptions of an advanced leadership development system: It is system wide (not only business specific) and customer oriented (not only leader/participant oriented).