The UN Security Council (UNSC) confronts at least three challenges in translating its actions during armed conflict into more durable peace after conflict. First, heavy-handed interventions such as military deployments and sanctions can impede the ability of the disputants to identify and reach a self-sustaining settlement when there is insufficient follow-through. Second, coordination problems can arise in handing off peacemaking activities from actors in the Secretariat to the UNSC when post-conflict security guarantees and continuous engagement are needed. Third, explicit attempts by the UNSC to produce peace and stability make it susceptible to the problem of cheap talk when it proclaims its concerns. After characterizing these problems in theory and generating observable implications, the paper uses original data on UNSC resolutions to test the hypotheses. The results indicate that the UN can succeed as a short-term peacemaker, particularly when it relies on diplomatic engagement and sanctions. However, when there is not adequate follow-through in the form of peacekeeping, the UN struggles to improve the long-term prospects of peace in part because it tends to promote stop-gap ceasefire resolutions. With peacekeeping, active UN involvement during conflict can promote long-term stability. Half measures such as condemnations have little effect on the stability of peace.