Changing teaching practice is difficult. This difficulty is especially acute in the case of dialogic teaching, which intensifies the complexity and uncertainty of teaching, often requires shifts in teachers’ beliefs, and increases the demands on teachers’ skills, knowledge, flexibility and judgement. Developing dialogic teaching is therefore a formidable challenge for the individual teacher and can seem an insurmountable task for those seeking to enact dialogic teaching in a sustainable manner and on a wide scale. In this chapter, I discuss the challenges dialogic teaching poses for teachers, schools and systems, and the implications of these challenges for developing and sustaining dialogic teaching. I argue for a socio-cultural, situative, and ecological perspective on teacher learning that focuses on the epistemic and social resources and infrastructures that mediate teacher learning and practice, within and beyond professional development processes.