This paper examines how English for Specific Purposes lecturers changed their teaching strategies that align with their beliefs about active learning at a Vietnamese university. There is a growing interest in making changes in tertiary instructional practices to involve students in active learning in response to increasing international contexts. Significant reforms of higher education in Vietnam have called for the quality of education, particularly foreign language teaching and learning. Thus, it requires teachers to change not only thinking about new instructional ways but also role shift in improving student learning. However, there is a paucity of research into how science lecturers perceive their practice changes as improving student learning in interactive and dynamic ways. This paper draws on data collected as part of a qualitative action research study including interviews, classroom observations, and planning meetings over three-semester periods. The focus of this study is on the data which examined how five lecturers perceived and implemented active learning strategies. The findings indicate lecturers’ positive beliefs about the change process and their growing awareness of the need for role changes in their practices, thereby associating change with their agency in the change process. Pedagogical implications for policymakers and ESP lecturers are also considered.