In the past 25 years, 163 national constitutions in 64 countries have been newly adopted, or significantly amended during or following an internal armed conflict. A number of these changes to these conflict-related constitutions (CRCs) were instigated as part of a conflict resolution process, with active support from international actors. In fact, though still a rare phenomenon, UN peacekeeping operations and peace agreements sometimes even require constitutional reform, and the international community has begun to recognize the potential of constitutions as a conflict management tools. Constitutions are being used not only to rebuild the state after conflict, but also, with support from external actors, to help bring about a peaceful resolution to conflict in the first place. Given the significant influence that foreign actors can wield in such unstable contexts, understanding their impact is all the more important.The purpose of this study is to explain how and under what conditions international involvement in conflict-related constitution-making impacts outcomes. In particular, it address the following three related research questions: 1. Why do international actors get involved with some constitution-making processes and not others? 2. How does international support for conflict-related constitution-making impact constitutional substance? 3. Do constitution-making and international involvement contribute to the reduction of civil war recurrence?I argue that international involvement in constitution-making is not value-neutral. My argument rests on the importance of international actors as potentially influential advisors whose involvement in CRCs carries normative weight. I introduce a theory that sequentially addresses each of the three questions in turn. I introduce a novel dataset on international involvement in CRCS between 1991 and 2017. To test my arguments I employ cross-national statistical and necessary conditions/qualitative comparative analyses, as well as semi-structured interviews. I find that contrary to my expectations, peace agreements are not necessary for international involvement in constitution-making and that there is only limited evidence of an association between international actors and constitutional substance, using the substantive case of constitutional federalism. Both CRCs and international involvement are, however, associated with reduced conflict recurrence.