In this paper, we propose a model to explore how teachers learn pedagogical concepts in teacher education programs that expect them to become competent in lesson planning. In this context, we view pedagogical concepts as conceptual and methodological tools that help teachers to design a lesson plan on a topic, implement this lesson plan and assess its results. Concepts such as the notions of learning goals, errors, conceptual structure, representation systems, resources, grouping, interaction or assessment strategies are examples of such pedagogical concepts. We propose a model that involves three types of knowledge of a pedagogical concept—theoretical, technical and practical—for describing teachers' learning of it. The knowledge classification proposed by this model assumes that a teacher should know the theory about the pedagogical concept (theoretical knowledge), be able to use it for analysing the topic and producing information about it (technical knowledge), and be able to use this information for making decisions in the planning process (practical knowledge). We present examples of the development and enactment of those types of knowledge by a group of mathematics future teachers in a teacher education program we have worked on.