The paper looked at contextual factors that influenced the self-efficacy in teaching English as a Foreign Language (EFL) of a group of university teachers in Vietnam. Very little empirical research on teachers' self-efficacy in EFL contexts has been done and self-efficacy quantitative studies heavily outnumber qualitative studies. The present research took the form of a qualitative case study. Data collection tools included focus group discussions, individual interviews, journaling, and observations. Findings suggest that there were certain features of context, e.g. the state of leadership practices and collegiality, which may have affected what constituted sources of efficacy information and how they operated. In addition, it is plausible that changes in context, e.g. teaching different kinds of students, led to changes in the way the teachers weighed and selected efficacy information.