The dialogic teaching approach has been studied widely, both empirically and theoretically. However, despite four decades of research suggesting that dialogical interactions promote student learning, it has been very difficult to reflect this in practice. Teachers' professional development programmes oriented towards promoting dialogical pedagogies have been based on sociocultural approaches centred on teachers' reflective analysis of classroom practices. Studies show that reflecting on pedagogical practices is necessary but insufficient to promote the desired changes. Beyond reflection, initiatives centred on scaffolding the practice with dialogic discursive repertoires have seen more successful results. This suggests that centring on the practice seems to be fundamental to change. Nevertheless, the theoretical basis has not been elaborated further to understand why centring on the direct scaffolding of practice would promote teachers' learning and pedagogical practice transformation. In order to account for the available empirical evidence, drawing on the works of Bakhtin and Vygotsky, the aim of this paper is to elaborate on a dialogical theory of teacher learning. Using this theoretical approach, different theoretical views of learning, teacher professional development programmes and the main tensions therein are discussed.