This paper provides a mid-term assessment of externally-led Security Sector Reform (SSR) during the United Nations (UN) led peacebuilding intervention in Timor- Leste. Despite initial difficulties, several core institutions, introduced by the UN, remain effective and were integrated into local practices. These initial security problems of the new-born Timor-Leste state, included the radical reconfiguration of the power balances within elites and an unfamiliarity with new approaches to security governance by the indigenous actors themselves. The lack of contextual knowledge and insensitivity to local political dynamics by external actors exacerbated these issues. Nonetheless, Timor-Leste has found ways to achieve some measure of political stability and physical security, both of which were always overarching goals of SSR.