Within research into the teaching profession, there are two main areas of interest, which have been thoroughly defined and consolidated: teacher’s knowledge and teacher’s professional development. This paper considers the latter area, and specifically sets out to define the concept of the reflective teacher and to show how we have applied this concept in our research. It aims at defining a more precise notion of teachers’ professional development linked to the concept of a reflective teacher, drawing on information from different interdisciplinary sources so as to frame the concept clearly. We discuss the conditions which determine the reflective teacher, and report on how these were put to use in a training course for practising teachers in which participants reflected on challenging episodes from their professional experience. We hope that clarifying this term will enable different educational agents (school teachers, teacher trainers or researchers) to have an informed view that can be interpreted and critiqued, and that it will also be of value to initial teacher training and to in-service courses.