This thesis explores the development of mental health systems in the Pacific Island Countries (PICs) of Samoa and Tonga through an examination of several policy transfer events from the colonial to the contemporary. Beginning in the 1990s, mental health became an area of global policy concern as reflected in concerted international organisation and bilateral aid and development agendas, most notably those of the World Bank, World Health Organization, and the Australian Agency for International Development. Tonga and Samoa both reformed their respective mental health systems during these years, after relatively long periods of stagnation. By undertaking a comprehensive investigation of the respective governments’ policy- and law-making processes from 2000-2007, this thesis identifies three distinct levels of policy implicated in mental health system transfer processes from developed to developing nations: (1) colonial authority and influence; (2) decolonisation processes; and (3) the global development agenda surrounding health systems. I use the policy transfer literature to explain these policy outcomes and expand it to include consideration of the historical institutional dimensions evidenced by contemporary mental health systems. These policy levels include (1) formal policy transfers, which tend to be prescriptive, involving professional problem construction and the designation of appropriate state apparatus for curative or custodial care provision; (2) quasi-formal transfers, which tend to be aspirational and involve policy instruments developed through collaborative, participatory processes; and (3) informal transfers that tend to be normative and include practices by professional actors in delivering service merged with traditional cultural beliefs as to disease aetiology as well as reflecting a deep understanding of the cultural context within which the services will be delivered. I conclude that informal policy transfer through information-sharing, training and social networks effectively delivered the values of the respective mental health systems many years prior to formal or quasi-formal transfers. The informal transfers involved medical professional policy entrepreneurs influencing service delivery practices to their respective community-based service visions. These informal transfers were marked by a high degree of hybridisation of international and indigenous mental health best practices. Formal and quasi-formal policy transfers, by contrast, occurred only with the direct intervention of foreign experts.