Leadership development has traditionally encapsulated an individualistic focus in organizations more properly construed as leader rather than leadership development. Over more recent years, advances in leadership theory have moved towards seeing leadership from more relational and systemic perspectives that have implications for leadership development practice. This article builds on this literature in putting forward a model of leadership development drawing upon ideas and concepts from complexity science. Complexity leadership development is suggested to incorporate a focus on four key dimensions that recognize the interrelatedness and systemicity of leadership in organizations. Here the behaviours of individuals interact with wider organizational processes and contexts that together are considered to produce overall leadership effects. Four dimensions are put forward in the complexity leadership development model comprising (1) network conditions, (2) shared leadership, (3) organizational learning and (4) leader skills and knowledge. The implications of the model for future research in HRD and challenges for practice in the field are discussed.