P(p)ublic A(a)dministration is influenced by multiple factors, inclusive of complex policy issues, multi-faceted forms of accountability and hybrid governance models. Consequently, public administration organisations must strengthen their adaptive and complexity capacity to deal with environmental complexity through adopting a different leadership model that is characterised by distinct but complementary leadership functions. Complexity leadership theory (CLT) is thus adopted as an appropriate theoretical lens for the study due to its integrative, collective and relational approach to leadership, in spite of its limited application in the public administration context. Against this background, the purpose of the study is to apply CLT as the basis to determine the required leadership competencies that should underpin a complex adaptive system such as the Governance and Administration (G&A) Cluster of the South African government because of concerns regarding the unevenness or lack of appropriate leadership competencies, behaviours and skills to make the government cluster system effective. To address the purpose of the study and the underlying research problem, a mixed methods research approach was adopted to investigate the leadership competency implications of Public Administration reforms plus their links with intergovernmental relations developments, and the implications of the transition from leader-centric practices to collective and hybrid forms of leadership. An analysis of existing literature in these areas leads to the conclusion that the G&A Cluster, which is an intergovernmental relations structure, is an integral part of hybrid organisational arrangements whose effectiveness requires a different approach to leadership. The literature analysis further identifies a disjuncture between leader-centric practices and conceptions of leadership as a collective, collaborative and hybrid phenomenon. The disjuncture is attributed to the scarcity of leadership and competency-based management (CBM) literature to guide the development of complexity leadership practice, especially in inter-organisational arrangements, and reliance on theoretical analysis as the basis to propose competencies for complexity leadership. Thus, the study addresses the research question and simultaneously contributes towards knowledge and practice by providing an empirical lens to the dynamics of collective leadership in a government inter-organisational structure and advancing CBM through articulating seven adaptable principles and six competency clusters that inform the development of a meso level leadership competency framework for inter-organisational arrangements. The study is also contributing to the application of CLT in P(p)ublic A(a)dministration and improved understanding of CLT’s leadership functions by clarifying its competency dimensions. The study concludes with an outline of implications and recommendations for inter-organisational leadership competency development and practice as well as recommendations for further research. / Thesis (PhD (Public Administration and Management))--University of Pretoria, 2021. / University of Pretoria’s Faculty of Economic and Management Sciences (2019-20210) Office of the Public Service Commission (2021) / School of Public Management and Administration (SPMA) / PhD (Public Administration and Management) / Unrestricted