Much organisational decision-making is embedded in hierarchical structures and leadership, even though hierarchies are limited in how they deal with increasingly complex issues. This paper explores links between identity formation, and the subsequent development of shared leadership. It explores how a programme to develop shared leadership changed a public science organisation, from one dependent on hierarchical leadership, to one that also used shared leadership to better address the complex public context. Using Day and Harrison’s levels of leadership identity framework, this study first examines the processes of a development programme at individual, relational, and collective levels. Results reveal cascading growth in leadership identities through processes such as job crafting and contagion. Despite the resulting positive processes, inherent paradoxes of power, goals, and attitude underlying shared leadership development are also identified. Within these paradoxes, tensions between vertical hierarchy versus dispersed networks, task performance versus job crafting, fatigue versus revitalisation, and cynicism versus evangelism were found.