Biometrics is a technology that is increasingly being adopted by armed forces. It is the automated recognition of individuals based on their biological or behavioral characteristics. Important questions in relation to the use of this technology by armed forces concern the legal framework that governs such use. This article discusses the relationship between International Humanitarian Law (IHL) and biometrics, by focusing on a number of different activities carried out during armed conflict in which biometrics can play a role. It concludes that although IHL contains no rules that expressly regulate the use of biometrics, a number of IHL rules are relevant to such use. Some IHL rules may require the use of biometrics under certain circumstances, while others may limit such use. The application of IHL to biometrics raises a number of questions of interpretation, and thus lack of clarity. It is submitted that a discussion among States is required before determining whether new rules are required to address that lack of clarity, or whether clarification of the law will suffice. A first step could be the drafting of a document with non-binding "best practices."