While it is widely accepted that punishing the perpetrators of violations of international humanitarian law is an important instrument in improving compliance with the law, little research has been done into the obligations on armed groups to impose sanctions and their possibilities for doing so. This article discusses characteristics of armed groups that influence their willingness and ability to comply with international humanitarian law and to punish those of their members who commit violations. It takes a holistic approach to these sanctions, and analyses the different methods of punishing members of armed groups, including disciplinary sanctions, penal sanctions imposed by the state and penal sanctions imposed by the group itself.