To what extent can ex-combatants meaningfully engage in peace-building in protracted conflicts and post-conflict contexts in the Middle East? What are the assets and liabilities that former fighters bring to peace-building initiatives, and what does their involvement look like in practice? What lessons from ex-combatant peace-building efforts in post-conflict settings are transferable to active conflicts? In this paper, we explore the role of former combatants in the case studies of Lebanon and Israel-Palestine. We first argue that, while former combatant involvement in peace-building is controversial, it is this same contentious identity that gives initiatives driven by ex-combatants the salience and leverage that other peace-building endeavours often lack, especially in communities that remain divided. Second, we argue that ex-combatant involvement in peace-building necessarily ‘looks different’ in every context, and especially requires different approaches in post-conflict and active-conflict environments. Lastly, we argue that ex-combatant peace-building is most effective when it does not strive for reconciliation per se, but rather when it advocates for nonviolent means of political struggle and critical dialogue, and when it is integrated with other elements of community development. The findings of the paper are based primarily on semi-structured interviews conducted by the authors with ex-combatants in Lebanon and Israel-Palestine from 2015-2017. The interviews seek to identify both individual and collective motivations, objectives, and experiences of ex-combatants with peace-building, and are coded and analysed to locate differences both within and between the case studies. As many of the participants in the study are members of the groups Fighters for Peace (Lebanon) and Combatants for Peace (Israel-Palestine), our findings also draw from participant observation at events hosted by both organisations in their respective locations. We situate our fieldwork findings in the interdisciplinary literatures on nonviolence, identity, and conflict transformation, as well as research on the roles of ex-combatants in other conflict contexts.