Abstract: This article examines the emergence of the UN Treaty on the Prohibition of Nuclear Weapons from a critical perspective, including how and to what degree efforts to alter states’ framing of nuclear weapons was a factor in the treaty’s emergence and negotiation. It examines the so-called humanitarian initiative on the consequences of nuclear weapons, the activities of the International Campaign to Abolish Nuclear Weapons and the roles played by transnational institutions like the United Nations and the Red Cross Movement. In view of this case, lessons and limits on transnational advocacy network models of norm emergence are highlighted. In order to contribute to the process of better understanding the emergence and significance of the prohibition treaty process based on research, some areas are identified in which evidence gathering and theorizing are needed.