In light of the forthcoming transitions in the Democratic Republic of the Congo and in South Sudan, this study looks at Côte d’Ivoire and Sierra Leone as two historical examples of United Nations peace operations being involved in security sector reform (SSR). It analyses both cases and makes recommendations based on 11 factors for success or failure of SSR processes and the transition of activities: (1) context awareness of the UN in support of SSR; (2) nature and timing of the UN transition mandate regarding the status of SSR; (3) inclusion of the principles of good governance in the SSR process; (4) acknowledgment of multilevel governance and willingness to engage with non-state actors; (5) national and local political leadership and commitment to SSR; (6) level of embeddedness of the SSR process in broader recovery frameworks; (7) civil society involvement in support of local ownership of SSR; (8) application of a gender-responsive SSR process; (9) linkages and synergies between the SSR process and the DDR programme; (10) involvement of external non-UN actors, donors and partners in the SSR process; and (11) availability of sustainable funding for the SSR process.