This article introduces a novel concept, humanitarian security regimes, and enquires under what conditions they arise and what is distinctive about them. Humanitarian security regimes are driven by altruistic imperatives aiming to prohibit and restrict behaviour, impede lethal technology or ban categories of weapons through disarmament treaties; they embrace humanitarian perspectives that seek to prevent civilian casualties, precluding harmful behavior, protecting and ensuring the rights of victims and survivors of armed violence. The article explores how these regimes appear in the security area, usually in opposition to the aspirations of the most powerful states. The existing regimes literature has mostly taken a functional approach to analyzing cooperation, lacks a humanitarian hypothesis and does not explore the emergence of new regimes in the core area of security. The author argues that in the processes of humanitarian security regime-making, it is the national interest that is restructured to incorporate new normative understandings that then become part of the new national security aspirations. Thisarticle intends to fill this gap and its importance rests on three reasons. First, security areas that were previously considered to be the exclusive domain of states have now been the focus of change by actors beyond the state. Second, states have embraced changes to domains close to their national security (e.g. arms) mostly cognizant of humanitarian concerns. Third, states are compelled to re-evaluate their national interests motivated by a clear humanitarian impetus. Three conditions for the emergence of humanitarian security regimes are explained: marginalization and delegitimization; multilevel agency, and reputational concerns.