Given the fundamental role beliefs play in guiding what individuals think and do, it is important to understand teachers’ beliefs and their development in order to facilitate professional growth, which in turn has the potential to promote effective teaching and learning. While research efforts have been devoted largely to investigating teachers’ beliefs, it is surprising that, despite its significance, there is little published data concerning vocabulary teaching, not to mention how professional training contributes to teachers’ change in relation to the language area. This thesis, therefore, seeks to investigate teachers’ epistemological and pedagogical beliefs about vocabulary development, understand their relationship with actual practice, as well as exploring how they develop through a dialogic approach which emphasises interaction and self-reflection. The study reported herein is situated in the context of Hong Kong, where problems relating to the teaching and learning of English vocabulary have been repeatedly highlighted in the literature. It mainly involves six frontline teachers of English as a second language in a local secondary school selected using purposeful sampling. Of these six teachers, four participated in a teacher development programme which focused on dialogic reflection on beliefs and practices regarding vocabulary teaching, whereas the remaining ones did not. Adopting a case study research strategy, the research draws on four major sources of data, including lesson observations, semi-structured interviews, teachers’ professional dialogues and reflective writing, to illuminate issues regarding vocabulary teaching and the process of change.

The findings of the study reveal the need to promote teacher professional development regarding vocabulary teaching and develop teachers’ awareness of their own and alternative beliefs and practices. They also provide empirical support for the notion that dialogic reflection helps foster teachers’ change, and enable us to arrive at a better understanding of the complicated nature of teachers’ cognitive and behavioural development. These shed new light on sociocultural theory, generate original insights into how dialogic interaction can be used as a mediational tool to facilitate and understand teacher change in beliefs and practice, as well as providing implications for second language education and teacher professional development.