The transition from war to peace is seldom smooth, and violence persists in many postwar societies. Existing research found that peacekeepers have a good record in addressing postwar violence along the fault lines of the preceding conflict. Yet, most postwar violence stems from actors that were not formally part of the conflict. The shift of actors is a challenge for peacekeepers focused on keeping the peace between the belligerents. Nonetheless, recent studies show that only UN police positively impact postwar violence, likely due to their broader effect on public security. Further scrutinising this finding, the research question is How do peacekeeping mandates impact the level of postwar violence in the aftermath of intra-state conflicts? I argue that variation in peacekeepers’ activities sheds light on how peacekeeping missions address postwar violence: Missions with public security-oriented mandates can reduce postwar violence better than other missions because they fill the public security gap. I test this hypothesis utilising a quantitative research strategy of 310 post-conflict episodes – years of60 conflicts between 1991 and 2016. The results imply that public security-oriented missions might not prevent collective strategic postwar violence but positively impact spontaneous unorganised postwar violence.