Teachers are increasingly acknowledged as active change agents or active learners who participate in the process of making sense of the new reform, rather than merely consumers or adopters of the policy. This interpretive case study, therefore, explores the dynamic interplay among teacher identity, teacher agency and the context as these condition how EFL teachers experience the curriculum change for upper-secondary education in Vietnam. Qualitative data were derived from multiple interviews with classroom teachers and school leaders, complemented with classroom observations and related documents. The findings of this study revealed that the teachers’ professional identities were mediators in relation to their interpretations and responses to the curriculum. The teachers’ perceptions of their professional identities were shaped by their prior learning and teaching experiences as well as the socio-educational context in which they lived and worked. The study concludes with implications upon which curriculum policy reformers and other associated stakeholders can draw with hope to better inform the design and practices of curriculum policy and professional development activities.