English language as a compulsory component of primary state school curricula is a growing phenomenon around the world. One of the challenges of this lies in training the vast numbers of teachers required. To date there has been little consideration of how those tasked with facilitating the professional development of primary English language teachers might be supported and the kind of knowledge, skills, and understanding they might need. This paper explores the experiences of primary teachers and university lecturers learning to become in-service teacher educators in the context of primary ELT curriculum change in Vietnam. The findings provide insights into the participants' understanding of primary English language teaching and learning and the new curriculum, their awareness of the classroom contexts in which primary teachers work, and their ability to support teachers in implementing the innovation. The implications of this beyond the context of the study are highlighted.