International humanitarian law forms part of international criminal law. The international criminal law of war crimes in turn forms part of international humanitarian law. International criminal law and its application through international criminal tribunals (international criminal justice) are increasingly important for the implementation of international humanitarian law. In this contribution, the author tries to define and differentiate the two branches. Particular emphasis is put on the influence of international criminal law upon international humanitarian law. The former has contributed to the implementation of the latter in general and to the development and clarification of the substance of the latter, but that viewing international humanitarian law through the lens of international criminal law also entails risks, which are discussed in this article