The UN Convention on the Rights of the Child (1989) remains the most widely ratified international treaty on human rights. Since its completion in 1989, it has come to be seen as an authoritative statement on the human rights of children. Yet historians of human rights have so far paid little attention to the making of this document. This essay argues that the child rights convention – much like other treaties on the rights of specific groups – is of interest to historians, and not just because it recognized children as subjects of human rights. Many of the convention’s articles also challenged traditional boundaries between human rights and other areas of international law and policy. The essay examines in depth the debates surrounding the child rights convention’s Article 38 on children in armed conflict, a clause that has been widely discussed among human rights and child rights scholars because it failed to offer a strict age limit of 18 years for military recruitment and participation. What is rarely noted, however, is that Article 38 also marked the first time that a human rights treaty made a direct reference to humanitarian law, which in effect threw into question the conventional view that human rights law should not regulate the conduct of warfare. This essay illuminates in new ways the relationship between human rights and international humanitarian law.