The multifaceted nature of peace operations today and the increasingly violent environments in which their personnel operate increase the likelihood of their being called upon to use force. It thus becomes all the more important to understand when and how international humanitarian law (IHL) applies to their action. This article attempts to clarify the conditions for IHL applicability to multinational forces, the extent to which this body of law applies to peace operations, the determination of the parties to a conflict involving a multinational peace operation and the classification of such conflict. Finally, it tackles the important question of the personal, temporal and geographical scope of IHL in peace operations.Keywords: multinational operations, multinational forces, international humanitarian law, IHL, applicability of IHL.