Teacher agency in Vietnam is an under-researched area, to the cost of recognising teacher professionalism, the role of teachers in curriculum reform and, consequently, the success of important curriculum improvements. This paper reports on a multiple-case study investigating teacher agency in primary schools implementing the national EFL curriculum reform. Four teachers from different primary schools in one province in Vietnam were interviewed and observed in their classrooms. To give voice to these teachers, the findings are presented as storylines, revealing that they took differing paths of agency, which resulted in various curriculum outcomes. Working in low-resourced, policy-constraining contexts, the teachers revealed that they were exercising agency for the benefit of students and their own well-being. They mobilised available resources to act upon their beliefs and capacity. We argue that failing to recognise the presence and importance of teacher agency impacts on the quality of teaching and learning of EFL.