This article presents a case study of one particular lesson in which a teacher uses the features of an interactive whiteboard (IWB) to teach mental computation strategies to a Grade 1 class. The framework of Technological Pedagogical Content Knowledge (TPACK) is used to evaluate the teacher's use of the IWB to teach mathematical concepts to young children. The findings demonstrate that the TPACK framework can be useful in considering the mathematics knowledge required for teaching in the early years and helpful for describing teaching practices that incorporate technology. The study has implications for teachers and teacher educators who may use the framework to understand teaching approaches using technology with the aim of enhancing early years' classroom practice.